How to prepare roses for winter in southern Ontario?

Don't prune them now, that's a spring time job. All you have to do now is protect the roots, and you can do that a couple of ways. You can mound dirt around the base of the rose, or you can rake a bunch of leaves over there, and pile them around the roses, although, I prefer dirt, because getting those leaves raked up in the spring is a pain in the butt.

How to prepare roses for winter in southern Ontario?
Bon b 's answer is wrong. All flowering plants and trees should be pruned in the fall. Nonflowering plants and trees should be pruned in the spring. As for your roses, make mounds of dirt and mulch about 6-8 inches up from the base of the rose.