Insulate Roses Against Temperature Swings
In preparing roses for winter, the main factors that you're trying to combat include cold winds, alternate freezing and thawing, cold damage to the canes and bud union, and inability of plants to take in water when the ground is frozen. In this region, with only intermittent snow cover for insulation, alternate freezing and thawing is a particular problem. If you do nothing else, at least spread a loose mulch of leaves to keep the temperature stable around the plants.
Reduce Disease with Fall Cleanup
With a good fall cleanup of rose beds, there will be fewer pest and disease problems next year. Remove all leaves and other debris on the ground around the plants. Also remove the leaves left hanging on the plants. Apply a dormant spray, such as lime sulfur or dormant oil, to the ground and plants, following the manufacturer's recommendations.
Cover the Rose Crowns
Don't apply winter protection too early. Wait until you've had at least one really hard killing freeze. Usually anytime from mid-November until mid-December is best. Put a 6- to 8-inch mound of compost, mulch, or soil around the base of the plants. Make chicken wire silos that are 1 foot wider than the rose on all sides. Fill with loosely packed leaves, such as oak. Prepare climbing roses similarly and tie the canes securely to their support.
Think Ahead When Choosing and Planting Roses
One of the best methods of protecting roses in winter is to plant grafted roses with the bud union 2 inches deep. If you haven't been doing that, then plan on it for future rose plantings. Roses growing on their own roots, rather than grafted, have the advantage of being able to grow back from the roots if the top is killed back to the ground. Also consider growing hardy shrub roses that need little, if any, winter protection.
Overwintering Container-Grown Roses
Roses growing in a container are best overwintered if the container is at least 16 inches in diameter. Move the container into an unheated shelter away from cold winds. For extra protection, wrap the container in an insulating material, such as house insulation batting or bubble wrap. Don't forget to water the containers periodically during the winter so the soil does not dry out.