This is a disease of roses called "black spot." Not a very original name, but it is accurate.
for photos and advice about black spot and other rose diseases. The R.O.S.E. group also has pdf handouts you can print and take into the garden with you to learn about beneficial organisms (insects included) which will help your roses as well as remedies for diseases and harmful insects.
And welcome to The Helpful Gardener; I notice that this is your *very first* post!
Best wishes with your roses; please let us know how it goes. My roses and I have fought black spot many times due to the famous San Francisco Bay fog, so I know what it does to the plants...
Sunset Zone 17, USDA Zone 9