They're not completely single since they have two or three more petals, but for all intents and purposes they look single: Bermuda's Kathleen and Mr. Bluebird. I don't know that either would be hardy in your area but both bloom almost all the time. Betty Prior is another almost-single that I have and like. The true single I really adore is Mutabilis, and there again it's a warm-climate rose. Sorry, we're just in such different climate zones.

Ingrid

There are plenty I like, because I like single blooms in general, but My favorite would have to be mutabilis. Too bad those in the North can't grow it. Mine is growing up through a pyracantha tree. So the pyracantha looks like has big pastel blooms.

Oh i didnt realize mutabilis wasnt ok here! I had it on my chamblees list, and was really looking forward to it.
How about queen of the musks? Mozart? I see pickering has some lovely singles.
I dont mind the extra petals at all, i kinda like the openess of them in general! I love to see the bumble bees on them .

For your zone, check out La Belle Sultane (once-blooming) and Nastarana (actually semi-double, blooms in flushes). I like both of these a lot.

Here is a link that might be useful: La Belle Sultane HMF

I had the oldish Hybrid Tea 'White Wings' years ago and thought it was a lovely rose: I don't know how it would do for vigor and disease resistance in your area. Its petals closed in dark weather. 'Dainty Bess' is another famous oldish single HT, very pretty: same warnings apply. I believe there was a vogue for single HTs before WWII. 'Sally Holmes' is a big handsome shrub with good foliage, though no scent that I ever detected. Oh! 'Vanity'! a big, leggy, lanky Hybrid Musk with single shocking pink fragrant blooms, a very happy rose. How about 'Souvenir de St. Anne's', a semi-double sport of 'Souvenir de la Malmaison'? Fragrant, prolific, and handsome; a bigger plant than its sport parent, at least in warm climates.
If you have room for big, once-flowering species roses and their close kin, 'Fruehlingsgold' is very large and very beautiful, at least to my taste. It's fragrant. 'Canary Bird' is the first rose to bloom in my garden and is a handsome creature at all times (it colors well in fall) and there are other early species yellows. Some offspring from the species yellows: the famous Spinosissima hybrid 'Golden Wings'; its beautiful Austin-bred child 'Windrush'; and a rose I got from Germany, I don't know how available in the U.S. (Vintage lists it in their catalog), the lovely Foetida hybrid 'Wildenfels Gelb'. These hybrids should be somewhat less rampageous than their species parents. All the roses I list here are hardy at least through Zone 6b. I don't know about disease resistance or how they come through cold winters. Oh, yes, 'Alba Semiplena', a study in milk white and gray green, a lovely rose; and 'Dupontii', with similar colors. Both of these are fragrant and are dignified noble roses: large, once-flowering, but always beautiful. 'Dupontii' makes clusters of hips of an unusual dusky, peach-tinted pink, in keeping with the gray tones of the foliage.
I hope this helps.
Melissa

Melissa has listed some of my favorites in my own garden. Beautiful roses they are. Let's add ...

Kathleen, beautiful hybrid musk with blush pink flowers that look like apple blossoms. It is one of my best hip producers in the fall.

Schoener's Nutkana, a cross between a species rose and the HP Paul Neyron. It has the beautiful warm hot pink of its HP parent, and huge single flower form with bright yellow stamens. Once blooming, and worth the wait. One of my favorite roses!

Poulsen's Pearl, a floribunda with flowers that look a lot like Dainty Bess. It's making a name for itself on the show table, and was featured on the cover of American Rose magazine this summer.

Ellen Willmott. Early, single form, hybrid tea. Beautiful.

Mrs. Oakley Fisher. Another single-form HT. This rose is rarely out of bloom for me.

"Miss Lowe's Variety" a found China rose, in a gorgeous shade of warm red. Love this one!!

Mary Guthrie, a new-to-me hot pink polyantha that is fragrant. I think I'm gonna really like this one.

Silver Moon, a beautiful rambler with huge white flowers in late spring. Bred by Dr. Van Fleet, my favorite hybridizer.

Playgirl, a hot pink floribunda by my other favorite hybridizer, Ralph Moore.

Basye's Purple, picture a rose with blue-green foliage, cinnamon brown stems and canes, and velvet magenta-purple flowers ... and you have this spectacular rose. I have yet to get a photo of it that accurately depicts the gorgeous color of these flowers.

Happenstance, a miniature version of Mermaid. Yellow buds open to white flowers about 2" across, on a mounding plant with tiny leaves and no disease.

Pink Surprise is a huge rugosa cross (that lives beside Happenstance in my garden) It's thorny and vigorous, and totally beautiful. If you have a spot that can use a huge, mounding rose, Pink Surprise would be a fabulous addition to your garden. It's not growing tall for me, just spreading outward like a lava flow. Before I cut it back, it was three years old, 3 feet high, and 10' wide. I love this rose!

I think that's enough for now. I have lots more (singles are my favorite flower form). Add some to your garden, and you will love them, too.

Connie

I'm going to add some to this list as I really like singles and semi doubles too:

Darlow's Enigma
The Alexandra Rose (David Austin)
Bengal Fire (may not be hardy for you)
Pierre Gagnierre (a more modern Delbard climber)
Rosa Mundi
Erfurt
Amy Robesart
R. spinossissima
R. roxburghii
R. glauca
Clair Matin

Robert

"Darlow's Enigma" is a study name. Try 'Fruhlingsmorgen', it has a special beauty.

Second on Connie's Basye's Purple and on the Rosa Mundi suggestion. I also like Ballerina and the newer shrub rose Carefree Spirit. Betty Boop is not quite single, but I like it nonetheless; holds a place right next to my front walkway. I grow Darlow's, but it leaves me a bit cold with the large vigorous growth and the small white (unscented?) flowers; maybe it is too healthy for me to really care about?

On another subject, do you think Darlow's is scented? I get a little whiff but another EMG raves about the scent.

Here is a link that might be useful: Garden Musings blog

Mrs Oakley Fisher, Dusky Maiden, Pearl Drift, rosa primula, rosa moyesii, Shoener's Nutkana, Mrs Herbert Stevens, Meg, Duchess of Portland, Dairy Maid, Irish Elegance, R.Dupontii, R,helenae, Moonlight, Mermaid, Daisy Hill, R Sancta, R.Laevigata, Lagoon, Cupid, Frances E Lester, Dunwich rose, R hugonis, R cantabridgiensis, Altissimo, James Mason Euphrates, Sweet Haze, Euphoria.....could go on as I love the singles and semi doubles more than any other roses.

Hebe's Lip and Robbie Burns are tough but beautiful. Golden Wings is very nice, if you can grow it. I can't.

Trier rose is beautiful. I have two and they always seem to be blooming. I think it's a parent to the hybrid musk roses.

Darlow's Enigma is a very nice rose. Not much fragrance, unless I'm close up, but we have a very dry climate. If it's humid (like before it rains) it's much more fragrant.

Golden Wings is light yellow for me (although some of the web pictures showed it more white) but very charming. I'm going to move the two I have over by the Darlow's Enigma next year. I think they'll be pretty together :)

Here is a link that might be useful: Trier rose

I'm a season ahead of you. My quest started after I saw some really lovely singles and semi's at Cliff's EuroDesert roses AND in florabunda form factor with REPEAT, woo-hoo!

I dunno how "z6" Pittsburgh is and some of these roses are marked in HMF with the default 6b zone; however, if you look at parentage, that may help you out. Ditto your local fungus problems.

From Cliff's...
Salomi (oooh-la-la red, beautiful stamens)
Night Sky (cherry red, slight yellow in center)
Rosarian Gregg Lowery (brilliant true yellow that doesn't blow or fade, by Cliff)
Daisy'O (striking orange/yellow blend, by Cliff named after his mom)
Anne-Aymone Giscard d'Estaing (very pretty white)
[I planted these in the front of the house by the two tall pines next to the front steps where they will get lots of sun. I'm hoping they will be quite a splash as you walk in the door.]
Mrs. Robinson (pink & white blend, by Cliff)
Blue For You (don't have it yet, but splendid at Cliff's - I'm stalking him until I can get one ;-)

I also have Paulson's Pearl (Vintage) and it is *really* lovely.

Aïcha is one of the most popular semidouble shrub roses in Sweden.

Here is a link that might be useful: Aïcha (Pedersen 1966)

The tea rose Mme Antoine Rebe, which is just a year old in my garden (and getting huge!) is so beautiful. Not many blooms yet but they are so lovely.

Love singles. My fav singles at the moment are Lavender Spoon (needs to be grafted for vigor, Burling does it), then Bukavu and Anne-Aymone Giscard d'Estang. Blue for You is not a single, but it's a favorite too. Keep pestering him, lol, it's worth it.

For anyone who says Darlow's Enigma does not have a scent, try this -- cut a big spray or two that still has some buds to open and then plonk it into a vase and put it in a small room and close the door -- e.g. the bathroom. The next time you open it, the scent will knock you over. That said, I have not smelled much of this one while blooms were still on the plant -- the scent seems to develop as a cut flower. I have several roses that do this, so it is a good experiment to try, just generally. Another one that gives off its fragrance only when cut is the older hybrid tea, Honor.

Kathy

'Secret Garden Musk Climber,' for its fragrance:
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R. arkansana "Peppermint Candy," for its unique color and foliage:
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'White Surprise' for the purity of its white petals, its size, and its stamens:
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But there are so many others . . .

Jeri

the HT 'Dainty Bess', the mini 'Gizmo' & 2 shrubs 'Robusta' & 'Lena' a 4 of my favorites

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I once ordered the single red rose Altissimo and got a different rose. It grows and has blooms exactly like Altissimo, except that the color of the blooms is different. The buds are a deep red/orange, then opening they are a beautiful coral/peach color for a long time, and then they eventually fade to a pale pink.

I think it is a sport of Altissimo that I have seen called Orange Altissimo, or Kathleen. I'm not sure about that, as the flowers are never actually orange. However, they are gorgeous, and the same huge size as the normal red Altissimo blooms. I think they are much prettier as they change colors.

Jackie

I have a coral sport of Altissimo named Christine. Heirlooms sells it and it is gorgeous, and not quite as tall as Altissimo, which is good.

Thanks Kathy - I mis-remembered the name, it is Christine, which HMF says is the same rose as Orange Altissimo. I got mine from Herilooms when I ordered Altissimo, so that probably settles it. 100% of the pictures on HMF are a solid, dark orange, however, which confuses me. As I said, mine is never that color, and when it first opens and is darker, it is still a peach/coral color. Maybe the soil, or something.

I don't know how tall Altissimo gets, but my Christine gets plenty tall for me - I just pruned it because it had jumped over our fence (along with Cl. Ice Berg - maybe they were eloping?) onto the next door neighbor's garage roof, and the neighbors are about to paint their garage. Luckily we have a good relationship, so they communicated with us, and I and my DH just spent all morning pruning our two thugs & tying them back onto the arch they are supposed to be growing on on our side of the fence. There were parts of Christine which were at least 15 feet high (or would have been except that part of that length was when it was horizontal making its escape attempt). Plenty big for me! My intent is that both of these roses will grow from their arch up our 3 story house, which should give them plenty of room to expand upwards.

Jackie

Today my friend Lesli (who I met on this forum about ten years ago) and I visited Antique Rose Emporium in San Antonio and while there I noticed this rose for the first time. It is VERY pretty! If you like stripes and singles it's one that bears watching.

Deana Krause ...
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This one was in a pot. I'll be eagerly watching to see how it looks if and when they plant it in their landscape.

That's right up my alley!

Jeri

There are so many most of them favorites. But there is one characteristic that might be something to sort out the best. And that is how does the bloom die? With a god awful brown set of stamens or endlessly clinging brown petals. All of which detracts from the simple beauty of the new open flower. I'm a nut about that. So I look for ones that die gracefully!

I love, love, love my Bishop Darlington.

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Eva
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Roxburghii Hirtula
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Like a fine piece of silk Mutabilis
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I really love
Complicata
Alba Semiplena
Rosa Mundi
Canary Bird
Primula
Hugonis
Lyda
Baby Balerina
La Belle Sultane
Alan Blanchard
Darlow's Enigma
Mutabilis

Olga

I have Dainty Bess, Bishop Darlington, La Belle Sultane, Windrush, Windmill, Blue for You, News, and this Austin rose, Morning Mist. How a rose as simple as this one could have as much fragrance as it does is a mystery, but I like it. I think it will be a large plant by its first year growth habit.

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Perhaps this one will tickle your fancy.

Oh my, how am i supposed to choose? I am now thinking how to make more room for a bed of these roses, rather than just a couple like i was planning. Bishop darlington is so pretty, so is trier rose. I really like the looks of mutabilis, and hebes lip is perfect because i have a statue of hebe on the way and i feel like i need that rose! i think this has been such a wonderful post, thank you all for the responses. It sure has given me alot to think about!

Rosa macracantha is a great looking single with a large bloom. Larger than most species roses. And quite cold hardy.

On the whole I am not a big fan of singles, preferring opulent cup-shaped roses. However, I am simply blown away by the incredibly fragrant Rosa moschata, Shakespeare's musk rose. Not only does the scent float on the air, but it blooms continuously for months starting in midsummer. Unfortunately, it is not a cold climate rose. I don't know if you would be able to grow it in a sheltered spot or not.

Rosefolly

If you have a lot of room, you could track down a plant of the 'Trier' x 'Mutabilis' seedling 'Plaisanterie' - it's one rose that totally shows it's heritage of both parents.

It's gorgeous, hardier than 'Mutabilis' and also cleaner here in Maryland in terms of disease resistance so far. Definitely more of a climber, but the flowers are exactly the coloring of 'Mutabilis', perhaps even pink/peachier and contained in the petal form of 'Trier' in that charming multiflora manner.

I love it.

Here is a link that might be useful: Plaisanterie on HMF