Originally Posted by Smallaxe
I had black spot real bad on a particular rose for years... then I moved it out into full sun and plenty of open air, which solved the problem completely...
It can help. It depends on the climate and the rose though.
They say to prune it to get more airflow between the leaves, to prune back any growth near the ground (where splashed rain water can bounce up onto the leaves), and to use mulch to prevent splashing.
Oh, and don't water from above.
I've done all those things, and still, I have been battling the issue for years. I have noticed that the roses with the shinier tops of leaves, tend to be a little less prone to black spot. I guess that the thicker cuticle helps rain water roll off.