where do you live? I'll bet it's a humid climate, right? Here in Arkansas, blackspot is a way of life for rose growers; it is endemic. All my roses have it. You've gotten off to a good start controlling this. That's all you can do is to control it. It's a chronic condition. Remove the worst looking leaves but don't strip the whole bush. Pick up any infected leaves that have fallen to the ground beneath the bush. Be sure to spray the ground underneath for a radius of about three feet . Destroy all the infected leaves, don't put them in the compost. It's recommended to switch fungicides yearly, I've been doing this, and recently someone posted a tip that suggested switching in between spraying; one one week, another the next. I've also found it helpful to remove all the mulch underneath each year in the late winter when I cut them back And replace it with fresh mulch. I've also heard it's helpful to spray the bushes with dormant oil in the winter. I've not been doing that, but I will start this winter. If you do choose to alternate fungicides on a weekly basis, systemic fungicides last longer, so there will be more time between spraying. I'm currently using liquid copper. It works about as well as anything else I've tried. Good luck, and keep us posted!