grass has overrun my roses
All is not lost. You can reclaim your rose garden. Weed control options are hand weeding the grass, removing as many roots as possible, covering the area with a plastic or landscape fabric covered with bark mulch, careful use of an herbicide, or a combination of the above.
Prevent the current grass crop from going to seed by careful use of a string trimmer and hand cutting. Then water to make the ground softer and hand weed. Or read labels on herbicides to find one that is allowed for use around roses. Follow label directions to treat the grass. When the grass appears dead, or the area has been weeded, cover with a thick layer of mulch, that can be with or without landscape fabric underneath. Finally, it will be an ongoing project to monitor the weeds in the roses and deal with them promptly so it isn't an overwhelming problem again.
Here is a link to an article from the Pacific Northwest Weed Management Handbook, titled "Home Garden and Landscape Management" for more detailed information on weed management.
Thank you for contacting Ask an Expert.