For roses, remove the leaves and start spraying with a fungicide every 2-3 weeks. Roses are very hard to grow in my area. The conditions are just not right for it here. I had to make to sure to feed with a systemic feeder every 6 weeks and spray the fungicide every 2 weeks and I still had issues with growing them. I finally gave up and admire my father-in-laws roses when I visit Portland, OR.
If you visit a big box store, they will have ready to use rose fungicide and concentrate.