In the long haul, you're GOING to want to mulch the area.
But I think you could dig holes, drop in the roses, and then mulch over that area of grass.

I actually did this 23 years ago, (and we have horrible Bermuda Grass) and it worked.
But if I were to do it over, I'd try to kill that area of lawn first.

Jeri

I noticed the shade beneath the tree, I'd check from 8 am to 5 pm as to how many hours of shade there is in the area where you wish to plant your rosebushes.

Where I garden, large flowered roses need between 7 and 8 hours of full sunlight to bloom well, except for
China, Tea, and Noisette roses of which all are slightly shade tolerant and bloom well with only 6 and 1/2 hours sunlight in our latitude, as are the small flowered Hybrid Musk rosebushes, where I live near San Francisco.
-Have you done a ph test? The answer will indicate what you should amend the soil with, if needed, if it turns out to be too acidic or alkaline for roses.

Lux.

chinatreasures, first of all, where are you?

I had St Augustine and also think it's beautiful when it's healthy. I don't have it anymore since my whole (very small) yard is either rose beds or path areas. I tried to keep a round area in the front yard with grass, but the St Augustine was just too much for me. It was monster grass where I need something much more demure. I used RoundUp and mulched on top of the dead grass for a few months, hoping it would decay. Yeah, right. It hadn't even begun to decay when I dug it up.

If you kill the grass in the whole area, you really only need to mulch the finished planted area as you go along. I would use some weed preventer (like Halts) in the killed area while it awaits planting.

You have a lovely location and plenty of grass to admire so I don't think you'll miss the St Augustine. Which roses are you planting? The up side of preparing a large bed is that you'll be ready for all the future roses that you'll be compelled to buy - just plop them right in, no muss, no fuss.

Welcome to roses!!

Sherry

Thanks so much for the responses!
Jerijen, that's what I was thinking I could do - go ahead and put them in and mulch around them, then gradually mulch the grassy area.
Lux, I haven't had the soil tested but got some good suggestions when planting - add milorganite and Graco 13-6-6.
Sherry, I'm in Tallahassee (almost the GA border). The soil is good here, not sandy but some clay (less clay in this particular area).

The roses I bought are those that have been grown in this area for hundreds of years. I've had good success with others I bought from this organization, but I have never had a "garden", just a plant here and there.

The picture was taken during the morning and the area gets at least 6 hours of sun. I'll check it again tomorrow and make sure, but I know it gets the midday and late afternoon sun. The direction of the camera view is to the west.

Don't know how you feel about herbicides, but St. Augustine is quite susceptible to grass killers such as Grass-b-Gone and Grassgetter (fluazifop, or floozyflop, as Jeri says). It might take two sprays, properly spaced (I think two weeks apart), but it's gone after that. Much easier to control than the dread Bermuda grass.

I mention that because at some point you're going to want the grass gone. yes, you can make holes, drop the roses in, and mulch those areas, but it's going to encroach and you're going to get tired of dealing with it, in my experience. Grass killer only goes after the monocots (grasses), and doesn't affect the dicots (broadleaf plants), such as roses and most other ornamentals. I've had some damage to dianthus, but that's it. Roundup kills all kinds of plants.

I don't go around spraying chemicals on a usual basis, but stern stuff (perennial grass) sometimes calls for stern measures.
Anita

yep, try to get rid of some of the grass and maybe plant the roses in two clumps of 3 rather than dotted around the whole space. Also, you can plant many things around the roses such as hardy geraniums - they are not keen on too much competition but many of us grow a lot of perennials round the roses. Making holes will work but that is an awful lot of fancy mowing around you are going to have to do so try to keep the roses in more of a cluster if you can.

I've done both - worked with just planting holes, and removing the grass beforehand. I recommend removing the grass beforehand. The easiest way I found was with a sod cutter. Really easy (a little hard to turn), very quick, and the bed I did that with is so much easier to maintain than the ones I tried to round-up. Obviously I missed some of the grass with the round-up and it grew, accidentally oversprayed round-up on the roses and it took them all summer to get normal growth again, and the grass is hard to weed around roots of the roses.

Yes, the sod cutter was work (actually got DS to do it for me), and it cost me a day of rental (about $65 if I recall correctly), but well worth it!

Also wanted to say that a lot of pre-emergent weed killers (in case you use that) are very harmful to fish.

As a previous owner of St. Augustine grass in central Florida, my advice is to kill it with RoundUp. Believe me, you can't kill the stuff no matter how much mulch you put over it.

Chinatreasures, I now have some land and have moved to Live Oak, so you aren't too awfully far from me. I am absolutely thrilled with the soil up here! Most of it is loam, although I do have some areas with quit a bit of clay.

You have a very lovely spot to plant your rose garden.

Sandy

Thanks for all the suggestions. I won't use any chemicals to kill the grass due to the close proximity to the lake which was recently "renovated". Carp have been added to eat the grasses - I don't want to upset any balances that may be going on in the lake. I think I'll just dig out the spaces where the roses will go, clustering them like suggested instead of spacing them out and mulch around the bushes. Then, remove grass and mulch as the garden grows. Y'all have been so helpful and I'll try to keep you up to date as the year progresses!