That black spot can be a huge problem to deal with. The only product I have found that will stop it in its tracks is called Mancozeb. It does leave a yellowish powder residue on the foliage but that is part of how it works. I spray the roses three times 7 to 10 days apart with it. Then go back to the regular fungicide of choice, which for me is called Green Cure. I get the Mancozeb from http://www.rosemania.com . The Green Cure you can get on-line too by just doing a search for it. The black spot does not disappear from the infected leaves but if it is dead after the sprayings, any new foliage should be free and clear of it. If you live in an area where black spot likes to get going, keep the rosebushes sprayed with your fungicide of choice and even apply some Mancozeb every third spraying to keep things under control.
