I make up my own spray - got it from an old organic rose growing book I found somewhere -- it changes the pH on the leaf to make it harder for black-spot to grow. 1/3 part milk, 2/3 parts water. A few drops of dish soap, A few drops of vegetable oil. A couple drops of vinegar (optional). The milk to water ratio does not need to be exact. Keep the remainder of the spray in your fridge - it's ok for the milk to turn sour - good even. Spray often, especially in humid weather and after a rain. Been using it for years, and it seems to work pretty well. If the weather gets too humid, then I do sometimes supplement with other commercial sprays.
