Begin winterizing roses after several hard frosts but before the ground freezes. Start by cleaning up debris around the plants to prevent diseases from overwintering. Mound soil or compost 8-10 inches high around each rose plant, using fresh soil to avoid damaging roots. Once the ground freezes, add a four-inch layer of mulch, such as straw, leaves, or wood chips, over the mound and secure it with soil. Prune canes to 36 inches, remove weak ones, and tie the remaining canes loosely to prevent wind damage. In spring, remove the mulch and soil to restore the normal soil level.