My roses are in a very sunny location.I live in Collingwood ON. Soil is loam.
The roses were covered by at least 5 feet of snow. I checked them yesterday and every stem is nibbled off right to the base.
How do I prune them and can they be saved? They have been giving me a lot of pleasure for the last 8 years
So sorry to hear about your rose damage. Although a thick layer of snow acts as an insulating blanket for plants it also provides a haven for rodents as well and these may have found your roses! Do not do anything yet until all risk of frost is past then try to prune your roses making a clean cut and mulch well around the plant. Your roses may resprout from the base although they may be smaller than previous years. During main growth period keep fertilizing them with rose specific fertilizer to build up vigour. For next winter you may want to consider protecting them with a barrier around the plant (like a collar) which may deter the rodents next time!
I hope your roses come back for you.