Where do you live? Has RRD been reported in your area? I would take a sample of the rose and bring it to the agriculture commission to have them determine if it is RRD or not. I would do as Christopher suggested and either use a miticide or soapy water to wash off the rose and then also sterilize your tools. For me, I would prefer a positive diagnosis from an expert before I started cutting down any bushes. Witches broom can appear for a number of reasons, not just from RRD.
