What shame! Your crepe myrtles are beautiful! Roses and trees are not usually compatible so I don't know what to tell you. Maybe you could do arbors with climbers on them instead!

well, there are trees and trees. While no rose would be happy cringing under a giant silver maple, there are many lovely redbuds, amelanchiers, rowans, which do sterling work. And then, what about shrubs - there is a lovely philadelphus much used in the UK, more for the golden foliage than for the blooms (although they still do, bloom that is)P.coronarius or the smaler leaved ones, P.microphylla. My own favourites, Deutzias and exochorda, grow well with roses and then you could go for something more productive and look at fruit trees - many in the same family (rosaceae) as roses. None of these mentioned have huge crowns so leaves falling everywhere in the pool are not a major worry, nor do they have overly aggressive roots.
Yep, you could opt for climbing roses, but nature is never happy in a monoculture so get a bit of tree diversity (and wildlife) in the garden.

That is sad, they are so pretty! My situation is similar to yours, the back yard faces south, with a wide curved bed along the fence, with roses. I have a red bud tree back there, and it doesn't bother the blooming. On the east side of the yard is another long, wide bed, and I have two still very small vitex that I'm trying to train as trees, don't know how that will work out lightwise!

Ogrose, my vitex went crazy with its roots in my rose bed! It was stealing all the water and soil for the rose I wanted near it. I ended up moving the rose and giving the tree more space than I had planned. It doesn't need much water, but man does it grow roots everywhere if it has some.

msjam, I think Italian cypresses would look gorgeous. Or a similar shape in your choice of color, lol. I'm using Irish Juniper in a particularly skinny form because they grow better here. Mine have grown very quickly and hardly ever need water!

I love the kind of formal look they give, although you can group them randomly, too and they are lovely like that. I have them in my hottest summer sites and they don't mind it!