Black spot on roses can be tough to get rid of. Some roses are resistant to black spot, which means that even though they get it, it doesn't affect the plant's overall health. I've got some like that, and I'm glad it doesn't kill them off, but it is unattractive. Especially if you also have rose slugs skeletonizing the leaves (my huge rose complaint). I've heard the best preventative for black spot on roses is starting treatment early, before it shows up, and continuing to treat throughout the growing season. There are a number of products out there. I've also heard from my favorite nurseryman that a solution of milk and water, and/or baking soda and water sprayed on them can help. You can check out Dave's Garden Web for info. They've got great folks in the forums with lots of knowledge.
My new favorite right now is one called Distant Drums. It's a shrub rose that looks like a hybrid tea. The bud starts out deep rose color, and then as it opens it lightens to paler pink, tan, and cream. It's stunning. Very very thorny, though. So is my favorite climber, Joseph's Coat, which shows a variety of yellow, orange, coral pink, and such all at once depending on how open the bloom is.
I tried a Knock Out rose last fall, and it's doing extremely well. That seems to be a super easy one to grow.
Love them. Yesterday I cut a bunch to bring inside, and it's so satisfying to see such beauty and know that I grew it.
gg