Answer: I don't think you will find a chemical weed control product that would not harm the vinca so if you can't pull the weeds out you might to just dig the entire bed, save the vinca for replanting and dig the weeds, roots and all. After you've done that you can apply a pre emergence weed control product to keep new weeds from sprouting in the bed. As for a new groundcover plant near your roses, here are a few perennials to consider:
Artemisia frigida (Fringed sage) grows 6-15 inches high; Yellow Late summer Blooms not showy, silver gray fringed foliage, woody stems;
Bouteloua gracilis (Blue grama grass) 12-18" tall, Clump-forming native grass. Callirhoe involucrata (Prairie winecups) 6-12", red flowers summer to fall. Cerastium tomentosum (Snow-in-summer), 6-8", white flowers spring to summer, Gray foliage.
Ceratostigma plumbaginoides (Plumbago) 8-12" Violet-blue flowersw late summer to fall; Shiny green leaves, purplish fall leaf color.
Delosperma sp. (Iceplant), 1-6" Red, yellow, white, fuchsia flowers, spring to fall; Succulent leaves.
Best wishes with your new landscape.
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