I'll try to comment thou I'm only in northern Illinois. wirosarium (sp), has some Kordes roses and perhaps will see this. The one problem is that some of these are new to the state but some have been around for quite a while.

I grow all of mine own root as that is what does best in my yard. When planting I place the rose so that where the branches start too form is about two inches under ground. Other than that I don't winter protect. Late fall winds usually blow leaves that catch on the bushes and I leave those where they have blown.

I would not be afraid to plant most Kordes in zone4 but thats me. I have a few that are tip hardy mostly from the vigorosa and baconia groups. Don't think they sell baconia here now I got mine from Northland Rosarium back when Carol had them. I wish they would bring this group back. They are fabulous roses.

The Veranda roses are vigorous and in my opinion should do well. They won't be cane hardy but crown hardy just plant deeply. In this series I have Cream, Jolie, Brilliant and Roxanne. Will get Chica when I find it. Blush will not open flowers in my zone and Brilliant will black spot but love it to much to care. It resides in my hot color flower bed.

The Fairy Tale series should grow in zone4. I have had all except Red Riding Hood. Shovel prune Brothers Grimm did not care for faded flower look. Best of the group for me Floral FT and Golden FT. Love these Floral FT as an own root is short front of bed rose. Golden FT is a 5 foot rose here. They are not cane hardy but crown hardy and like the Verandas are very vigorous and return year after year.

Kolorscape series vigorous and crown hardy should grow for you. I have all except Cheri and it's coming in spring. They are all beautiful and healthy roses. Biggest flowers on Lemon Fizz and Fire Opal.

Sorry to talk so much when I'm not in the zone you asked for. I'm hoping you get answers from zone4. One plug for Innocensia because its tip hardy after the worst polar winter. Short compact growth and easy for underplanting by larger roses.

I have about a dozen Kordes roses. Most from Palatines on multiflora root stock which I plant with the graft below ground. Seem to have decent winter hardiness with a little mulching, most of the above ground/mulch canes die back but they come back well for me and most seem to have decent BS resistance. Planted Lemon Fizz last year as an own root that I found at a regional big box store so waiting to see how that makes out. I have shovel pruned a few Kordes roses that didn't do good for me....Osiria--lacked vigor, several Freelander series (Kordes florist roses)--didn't like their blooms. Some of my fav Kordes roses are Antique Caramel, Pompon Veranda, Cream Veranda, South Africa, Lavaglut and possibly Lemon Fizz. I think you will have good luck with them in your z4 as well. Just remember to plant graft below ground & I even plant own root roses a few inches deeper than they were grown at the nursery. Here is a helpful graphic from the U. of MN:

Excellent graphic, thanks for sharing!

That great graphic also illustrates how I plant own root roses. Even if they come in pots.