Here is some non-specific information for you. You can ask the rosarian what would be best for black spot. I control mine with a good fungus control but I need to spray at least once a month if not more often. You have to make sure and get the underside of leaves as well as the tops. It's a pain to use a pump bottle so I have a small sprayer used ONLY for these kinds of sprays and I keep well marked one for weed killer. Not taking any chances!

Below the link is the formula I follow for feeding my roses. I'm not too gun-ho on Miracle Grow anymore, so I intend on adding more blood meal, bone meal and fish meal/emultion again halfway through the season.

Contact a Rosarian at the American Rose Assn.

WHEN TO START FERTILIZING ESTABLISHED BUSHES Immediately after pruning, incorporate organic amendments into the soil. As the soil warms with the weather, the organics will start to break down and supply a slow release nutritional diet to your roses, as well as feeding the soil micro-organisms. A basic recipe would include, per bush:
1 cup bone meal or superphosphate (0-20-0)
1 cup cottonseed meal
1/2 cup blood meal
1/2 cup fish meal
1/2 cup epsom salts (magnesium sulphate)
Water thoroughly first, then spread the ingredients evenly around the bush, under the drip-line (outer perimeter) of the bush. Scratch lightly into the top 1-2" of soil and water well again. In warm climates with long growing seasons (January-February pruning and blooms through November-December), a second application is beneficial in early September for fall bloom cycles.

About two to three weeks after spring pruning and adding organic amendments, new growth will appear. Chemical fertilizers, whether liquid or dry, can be applied at this time, and will provide an instant food source for this heavy feeding period. How often to apply is a subjective decision, based on the amount of time and devotion you have, but once a month should be the minimum.