The Bayer pellets or the drench don't really do a good job on blackspot. At least not here in Georgia :) You are better off using separate products. Bayer does make a fungicide spray that works very well on black spot. You can find it in Lowes. Normally you only need to spray every 2-3 weeks, but since you already have some blackspot, you may want to do it weekly until you don't see any new spots.

Combination products are not a good idea. You wind up putting down chemicals you don't need an they aren't effective for disease. I've attached a link to what you should buy. Bayer has so many products and the bottles look similar. Make sure you get the one that just says 'Disease Control. You can use it on the roses now. Just follow the directions about avoiding skin contact.

Here is a link that might be useful: Bayer Disease Control