Rose rosette disease is devastating to roses and will be extremely hard to control if it becomes widespread. Now is the time you might notice it on new growth.
The disease causes very red foliage and stems, copious thorns, "witch's broom" at branch ends and eventual death of the plant. It seems to be spread by tiny mites that travel on the wind. The only cure for it is to pull out and destroy affected plants.
- this article is a bit old (2001) but there is some good info on this disease. I've had it on a few of my rose plants here in NC, but I usually prune them out. It's definitely controllable if you prune regularly and properly dispose of the prunings.