All of our knockout roses have become infected with some sort of disease that I cannot identify. Nearly all of the leaves have turned brown and are falling off. The roses bloomed, and the browning started soon after. 

Several neighbors have the plants and I see no problems with theirs. we have plants in different parts of our yard and they all seem to be afflicted. Perhaps ours are a different type.

We would appreciate any advice on this issue. I'm considering either cutting them all the way back or just digging them up, but would love to save them if we can.

Thanks,