The roses may turn brown due to High humidity,too much concentrated fertilizer and not enough water in hot temperatures. Balling,thrips,over watered on the roots,malnutrition,climate problems.
There are a million things that could be causing it make sure there are no ants in the soil around the roots that happened to mine. If they get to much water they make them brown look closely at the leaves make sure there are no afids growing on them if there are get some lady bugs and put there.
This is probably a disease. My roses did the same thing. I read some books about it and found out it was a rose disease. You can go to a nursery and purchase a spray that will fix the problem.
