IMO, you can prune as far as you like in order to force basal growth and leaves further down. I would say maybe to 18" if you don't want bare legs. But I am very surprised that you had winter damage in South Georgia. Established canes of KO ought to be able to stand -5 F. Did the stems and leaves look normal last fall? Now?

Same thing happened to some Ko's in our zone but weather was much colder.
I'm also very surprised it happened in your zone!

I third the surprise at your roses having losses over winter.

The one planting locally that had comparable damage had major RRD problems. Their landscapers cut all the bushes way back late last fall and many died. The ones that didn't die have barely bloomed or grown this year. Other unscalped plantings (also with RRD symptoms throughout the bed) locally (almost identical conditions) had no damage over winter, so I wonder what problem yours had going into winter. Do you recall some bushes having slightly different colored blooms and more reddish colored foliage?

No damage other than yellowing leaves, which then got brown, kinda crispy in fact. The death seems to happen from the top, outside of canes and then continue down until the entire cane is dried out and dead. I should add we use a watering system as needed but that most of last year it was turned off due to so much rain.

The root systems are freaking amazing. They spread for ten feet or more and are healthy looking (I had to cut some to plant my new bushes). We have no RRD in my area that i am aware of and I saw no signs of anything odd other than the dead leaves.

We had a HUGE amount of rain last year. Enough that my Hybrid teas (in the same yard) defoliated and stayed that way even with spray. We had almost NO sun to speak of.

Winter was VERY cold for us, but this doesnt appear to be winter damage so much as something just causing entire canes to die, then the entire bush.....its something I have never seen before. They are single red knockouts. My double pink is 6 foot tall, 6 feet across. never defoliated. bloomed until Jan....its in the bed next to the hedge....I know I need to prune, and YES should have done it earlier, but I got so busy at work this hedge just got put on the back burner...btw, my Belinda's Dream Hedge is 8 foot tall already in the next bed, literally 4 feet from where the KnockOuts are.

My rosebeds are framing the parking lot of my shop on three sides, then there is a sitting area with a potted rose area on the opposite side of the walkway.

This is my double pink KO {{gwi:286712}}

This is the Belindas Dream, last year. {{gwi:286714}}

This is my shop parking lot. the top left of the photo you can a bit of the hedge. You can see where right in the middle of it there are new plants. That is where the ones died..if the entire area was in the shot, the lower left would be the Belindas Dream, and the DPKO is in the upper right. I was standing with the potted area to my immediate right, {{gwi:286716}}

{{gwi:286718}}

so everything is in close proximity....the only ones giving me a hard time are the KnockOuts in the hedge.....I am lost.

BUT I will be pruning them back this weekend and hoping that helps. The Belinda's Dream is headed toward getting "chopped" as well. It is own root and putting out lots of new canes from the bottom, so I need to top prune it...sigh....the work is never done! LOL

I do not have an answer for you but I sure do wish you better luck with the new ones you planted and hopefully the ones you pruned grow back much better!

I think for us in the SE, it was the combination of the cool wet summer we had and then the brutal winter. Everyone I know has lost not only roses, but all kinds of shrubs. On of my neighbors has a nice bed of hollies that have not come back. Usually these don't even lose their leaves.

I hear you about the Dr Huey roots. I had to dig up some dead roses and the roots (which were alive and well) were HUGE. I am sure I didn't get them all and will be fighting off suckers for awhile.