Snow is a wonderful insulator. We have none and it’s been 2 to 9 degrees at night. My roses have had no insulation. There’s not many left of the 40 or so that I had. Looks like there’s going to be even fewer next spring.
I think Home Depot carries bare-root roses in the Spring for people in just your situation. Also, you can loosely
bury your rosebushes in mulch and then burlap bag each of them to protect them from the frost monsters.
My mother did that when we lived in Massachusetts, and when we moved to California, she was delighted that
there was no need to do it there.