I live in Mn which is regularly colder than where you live but here is my experience with tree roses and David Austin roses.
Tree roses, if it gets sub-zero there, tip/bury them or they will eventuall go belly-up.
I dealt with them as a land-scaper and if they were not buried and covered well and it got to twenty plus below , while I did not lose any, they took a long time to come back.
You must tip and bury and cover heavily and then your fortune will be better.
David Austin, my brother planted four next to the garage, sunny side.
The garage due to warm cars inside, and good fortune, the area never suffered from snow drifts due to wind, kept the area warmer than open air.
As they were supposed to be hardy I put leaves around them and nothing else.
First year fine, second year one looked sickly, third year two went belly-up, fourth year I covered heavily.
Within six years they were all dead.
Just my experience.
