Black spot is an insidious fungus that hangs around and comes back once it's gotten started on a rose. Housekeeping is paramount to stopping it. You need to collect every leaf that has any spots, including removing them from the plant, and especially pick up every leaf off the ground to stop the spores from flying around and re-infecting your clean leaves.
I'd also use a baking soda spray to prevent infection of clean leaves. 1/2 tsp. baking soda to a quart spray bottle and spray it often because it washes off with sprinkling or rain. It won't 'cure' spots that are already there, but it changes the pH on the leaf surface so it's not hospitable for the fungus to start.
Make sure you aren't watering in the latter part of the day, also. Late watering that wets the leaves is an invitation to fungal spores to make themselves at home on the wet leaves during the night. Water early in the morning if you're using sprinklers that wet the leaves.
The whole infection may have started when you had a spell of really rainy weather earlier in the season. Btw if you will fill in your profile with your location, we'll have an easier time advising you, knowing what your weather and climate conditions are.