I would assume a tree rose is not as hardy to your area as a bush rose of the same cultivar would be, but you'd certainly have a much better chance with them than I would here in Zone 4! Bringing them indoors would not be a good option.
I don't think I would cut it back at all until you were able to see which parts are still alive in spring. Whether it would be worth keeping would depend on where it is grafted, assuming it is grafted, and where it died back to, if it does. I'm not an expert on roses trained as trees (standards) so I don't know how they are usually produced.