It looks like you are in agricultural or hardiness zone 4b/5a. This puts you on the edge of KnockOut roses hardiness zone. There are 2 things you should do to over-winter them: 1. Make sure the soil is moist right up until the ground freezes; 2. mulch the rose crown and rootball with 3-4 inches of mulch. Straw, pine boughs, chopped leaves and shredded or chipped wood are all fine. Snow acts as an excellent insulator. If winters are severe, you will have some winter-kill of rose canes. In early spring as the leaf buds are swelling or breaking open, prune back as far as needed to reach pith (inside of cane) that is white. I have had years where I needed to prune everything down to 12-18 inches. Even so, the roses roared back and were the same height as previous years by mid-summer. Here is more info: https://www.gardeningknowhow.com/ornamental/flowers/knockout-roses/care-knockout-roses.htm
Answered on October 19, 2018
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