I have very good luck with pelargoniums as companion plants to roses. I mostly plant common geraniums, but have some royal pelargoniums with my roses - and if anything, in my climate they're a little shy and slow growing comparatively.

When I find they get a little unwieldy, they have shallow root bases, and are easily pulled out of areas where they are not wanted, and hacked off to size. Super easy, and lots of color for me.