Never prune the main canes (the ones that grow from the base of the rose), unless it's to remove dead and damaged wood. Only prune the "laterals" that come off the main canes. And, you usually prune those when the forsythia's bloom in spring for you. You may want to check out Paul Zimmerman's video on utube about how to prune and control a climber. It will explain the concept of main cane vs laterals.
Are they going to be tied up on a trellis or fence? Mine are on a trellis and all I did, besides mounding the bases of the bushes with leaves, is I draped and tied burlap over the trellis to cover the canes. I worked like a charm for me! I didn't loose any canes over winter.
In the photo you can see (under all the snow lol!) that I draped the burlap over the trellis to cover the canes. I may work for you.

{{gwi:265681}}

Here is a link that might be useful: Pruning and controlling a climbing rose

If you *have* to cover a climber to get it through the winter, it isn't really a climber. Those varieties should be fine, even in a cold winter.

Given where you live, don't cover roses. During the inevitable warm spells, they will develop canker and other problems worse than the minor freeze damage.

Plant climbers that are hardy in your area. Winter-protecting climbers is a PIA and often not effective. Those varieties should be fine in zone 6b. Maybe in an unusual cold spike, you lose the upper part of the youngest canes.

Mine didn't get any canker at all. Maybe you don't need to mound up at all, but it doesn't hurt at all to drape a peice or two of burlap over the trellis. The ONLY reason I did it this year is because that rose is newly planted last year. I wanted to give it a chance to develop well before subjecting it to the cold winter winds here and such. This winter it won't get quite so much protection! Just a mound of leaves and mulch around the base probably.
It also depends on whether you are willing to let the rose grow back from the base each spring, if it dies down to the ground, and it would grow back, but for me, I WANT the really long canes for a very large trellis, so I have to try to protect the canes from the winds.

In NJ, protection will cause canker as Michael already mentioned. It could be OK in zone 5b, Ohio, but in warmer zone, protection does more harm than good. Both New Dawn and Rosarium Uetersen should be hardy in NJ. If they are planted with grafts below soil level, no mulch mounding is needed. Mounded mulsh will cause canker in zone 6 during warm temp.spells.
Olga

As others have said already, both those varieties should be mostly cane hardy in your zone.