I have May Night beside some yellow roses, but I wouldn't crowd them too close. Something lower growing or sprawling like geranium would be nice around the base of the rose.

If you don't plant May Night right below the rose, it will be fine. The color combo will be wonderful. I have May Night, catmint, rozanne geranium, and annuals allysum, lobelia and nasturtium growning around and under my roses.
Kathy

Knock-out is fairly low growing and keeps its lower leaves better then some - a benefit of disease resistance. May Night probably won't fit underneath, but could go along side. A low geranium is a nice idea, Rozanne is a nice blue, G. sanguinium var. striatum is a nice pale pink.

Ted

Concur that May Night is probably not a good fit. Under-rose plantings need to be of plants