belated thought, having gone back to reread your original post - if it's mainly a matter od keeping down weeds, have you thought about putting down a layer or 2 of landscape fabric around the roses, staying a foot or so away from their bases, and topping with a buncha mulch? Will require relatively little weeding. If that looks too stark, plant some decorative whatevers in holes cut thru the landscape fabric (between roses). If you mulch a lot and pull any weeds while they're small, it'll last at least 3-4 yrs before needing replacing.
The idea of groundcover plants as something that will radically reduce or eliminate weeding is often highly misunderstood IMO... relatively few kinds will grow *that* densely, and even those that will, they take a good long time to establish complete cover, during which time (years) you still gotta weed a lot.
Just a thought,
Pat