When is the proper time to cut back roses in zone 5?
I live in zone 5 as well. I wait until a couple good hard frosts have hit the rosebushes and the leaves are getting crispy and the canes showing signs of the cold damage. Then I prune most of the roses down to half their height and leave the hard pruning for early spring. Here is an article I wrote about it for you as well: https://www.gardeningknowhow.com/ornamental/flowers/roses/roses-winter-care.htm