Answer: In order to survive the winter, your tree roses will need to have their graft unions protected. Before you do anything to protect your roses, allow them to go dormant. In most northern climates this will be in November, usually around Thanksgiving, after cold weather arrives, but before the soil freezes to any great depth.
To protect them either make collars out of several thicknesses of newspaper to cover the graft, or wrap the graft with burlap. You could use fiberglass insulation if you have any on hand. The point is to keep the graft union from freezing and thawing when the temperatures are cold but the sun is warm. Remove the insulating material in the spring when temperatures remain above freezing.
Best wishes with your rose trees!
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