Check here infrequently, since this forum isn't much used & apologize for the delay in waving back. I'm near Charlottesville in the same zone maybe 20 miles East of the Blue Ridge. Grown roses for 30 years in cottage garden style, 15 of them here. Glad to be a sounding board for any questions within my experience!

I've learned ownroot roses do much better than any grafted here, shrugging off the freeze-thaw cycles so common in Winter & needing much less care in all respects. Your Knockouts are growing on their own roots so you're already ahead of that learning curve. Also depend on the 4 essentials of good health - soil, selection, siting & maintenance. And the fifth essential - good luck! My days of coddling roses are long past & they get the same general care as the rest of the garden once those basics are met.

Blackspot resistance is crucial here in the humidity, so reports of good health in similar circumstances help with selection. Each garden seems to have its individual mix of fungal varieties, so it often takes trial & error to find which roses succeed for you. But that's true for so many plants I just chalk it up to the gardening experience in general.

Roses healthy here in this organic no spray garden include climbers Golden Celebration, America, Aloha & her sport Dixieland Linda. The best floribunda here is Easy Does It. Must be a mix of 20 to 30 roses growing in these gardens. Best shrub rose is Ballerina out by the pond & seemingly oblivious to neglect beyond mild Spring pruning, All those named hold their green leaves through most of the Winter - another big plus for cold season grace.

Much more I could add to this brief introduction. Nice to meet you & you're welcome to pick my brain any time!