Most sources automatically list hybrid teas as zone 7 but that doesn't mean they won't winter in colder zones. If you look carefully at the garden tab on HMF for Sundowner you'll see that several people are growing it in colder zones. Even a couple in Illinois. The only way to know for sure is to try it. Try to find a nice wind protected spot to plant it and bury the bud union about 4 inches below the surface and maybe mulch it up a bit in the fall for winter protection and see how it does. You might be very surprised!

I
bought Sundowner at Menards 2 years ago and it has survived the two
brutal winters since with exceptional fortitude. Of course all HTs
and grandifloras die back to ground level in this climate (so plant
it deep--as Seil says) so the real test is how well they rejuvenate in spring.
Mine is already as tall and vigorous as any HT/grandiflora growing
among dozens. One of my best roses.

Read goncmg's comments in Columbus OH for details on how it wants to grow
tall, even in this climate.

Thanks so much for the input and link! I will give it a try, but oh my 7 feet in one season! I may have to pick a different spot for this one.