What should I do if rabbits are eating roses over the winter dormancy breaking period?

It depends on the kind of damage the rabbits have done on your cane. Roses break dormancy from a set of dormant buds on the cane and if the rabbits have chewed all dormant buds off, then the rose must essentially use their backup set of dormant buds. Those are usually further down on the cane which can be underneath the soil. It will break ground as it grows. You may get very limited leafing out on your old cane since the rabbits have chewed, that is not unusual. The best thing to do to repair severe animal damage is to apply a root stimulator.