I have never had galls on my roses, I do get leaf gall on my Azaleas, The treatment for most leaf and stem galls appear to be to do nothing or just remove the galls. For crown gall, which would be down near the base of the plant it appears the best thing to do is to immediately remove the plant and the soil with all the roots. It seems in most cases leaf and stem galls do very little damage to plants(in general).
I did find this article with some info on rose galls, about two thirds of the way though the article.
http://www.extension.umn.edu/g...
