You're right--blackspot doesn't form a border, nor does any other fungus disease.

For the dry yellow leaves, read up on spider mites (two-spotted mite) which are a chronic problem with indoor roses. Frequent sprays of soap or spray oil coating the undersides of all leaves may be needed-- or wash the plant down frequently with water. Mites will produce an overall bronzing of the older leaves with very find yellow stippling. The leaves gradually cup and dry out. Fine webbing may be visible. You can see mites on the undersides through a 6x hand lens.

Some roses naturally develop a dark border to the leaves, but this would be smooth rather than dotty. Dotty brown burnt-looking borders can be caused by too much fertilizer or other excess chemical salts in the soil. Salts may build up in potting soil over time, especially if a saucer catches and holds the drainage. Salts can be reduced by flushing with several inches of water. It's recommended to change potting soil every two years.

I'm not offering a firm diagnosis, just some things to think about.

I've seen also seen leaves like that after fertilizing--how much is too much seems to depend on the variety. Carefree Delight doesn't like to be fed liquid fertilizer, so it doesn't get any.

Interesting---I have a bit of evidence to support the fertilizer theory.

I planted my HT's in early May last year. They didn't get fed until much later....I think around the 2nd week of June. Coincidentally, that's when my shipment of mini's arrived. I planted the mini's in front of & between each HT, and saw the same type of browinsh/black leaf edges on each within about 10 days. They eventually recovered as they grew throughout the summer, but it was probably damage due to exposure to fertilizer on baby plants.

Ahh thanks very much for the information. I've been spraying for the mites but I will try to visually identify them the next time I have yellowing leaves and be sure. I wonder if I can photograph them somehow hmmm..

As to the border I will try to flush asap and maybe repot in a few weeks.

Thanks again!

I'd go with the fertilization theory. We see this here, in drought-years, when various minerals and the like begin to build up around the roots.
When it gets worse, we add a rim of white.
:-(

I'm overjoyed to say that we have had an abundance of winter rain, for once, which has flushed out the soil.
We should have a spring of good bloom and healthy foliage.

Jeri
Coaastal Ventura Co.,
SoCal

By now you should be placing your rose tree outdoors on days when the temp is over 35. Place the pot in a wagon and pull it inside a garage for the night. When outside, you can flush out the salts and spray the underside of the leaves to remove the mites.

This is the first rose tree I've tried to overwinter - I had no idea I should be taking it out when the temps were over 35. It won't be temperature shocked going from ~65 indoor temps to 35-40 all of a sudden? It was warmer than that today and it almost certainly should have been out today - but if it's around those temps it won't defoliate or anything?

Here is a closeup of one of the leaves on the tree - large version if you click through. Are these the spider mite markings you were talking about? {{gwi:233047}}From Plant Diagnosis
{{gwi:233048}}From Plant Diagnosis

Here's one of the yellowing leaves with a darker margin: {{gwi:233049}}From Plant Diagnosis

I will be sure to take it out tomorrow and flush the soil, spray down the foliage, and then use an insect soap in case the mites are back. Thanks again everyone!

Oh no. Something else going on there.
That light color (if it's correct) indicates something else going on -- and it's not chlorotic.

Jeri

Cut back on that fertilizer to half of what you're using now.
Spider mites will appear as very tiny salt and pepper like specks on the underside of the lower leaves. Watch them and you'll see them move. If washed off with a stream of water from a water wand every other day for a week, you'll break the propagation cycle. Spider mites suck the fluids out of individual cells causing the leaf to turn yellow and fall off.
Roses aren't as tender as you might think. As long as it doesn't get below freezing, yours will be fine. Just watch the temps and bring it inside before nightfall. Keep it out of cold winds. The temps drop quickly as the sun sets. Doing this will allow it to acclimate to the outdoors and natural sunlight.
I just removed several over wintered cuttings from a coldframe and repotted them. I left them out and placed them on a self in my unheated greenhouse. Even though it got to below freezing last night, they looked fine today.
How long has this rose tree been in that pot? Perhaps it's time to repot into a larger pot and with new soil!
If you can pull it out of its current pot without loosing soil from the root ball, take a look at the roots on the outside. If there's lot of tiny roots growing around in a circle, it's root bound. That won't explain the dark leaf edges but repotting may help.

The bright yellow leaf is just a dead leaf.

I haven't seen any mite symptoms in your pictures, but they would be expected on the oldest leaves first. They are nearly inevitable on indoor roses.