The main fungal disease for my area is powdery mildew.
In our exhibiting period, we sprayed regularly, to prevent mildew (and the occasional outbreak of blackspot.) We did that, weekly, until a dog we loved very much began to seizure, like clockwork, every time we sprayed.
That was it for us. Spraying ended immediately.
It took a full year for the effects of the chemicals to diminish to the point where the garden filled with beneficial insects, bug-eating birds, and lively lizards.
Any roses that could not, for the most part, grow healthily without chemicals were removed. And that is my "disease-control" recommendation.
It's taken a few years, but we have a healthy rose garden, sans any chemicals.