While roses in milder zones such as southern regions or California need very little winter preparation, those in colder regions farther north require much more winter protection. Too much winter protection can be more harmful than not having enough. Planting hardy varieties will lessen the winterizing measures needed as well. Most old roses are hardy, and new varieties that are hardy can be found in ARS Proof-of-the-Pudding reports in the The National Rose Society's "Rose Annual." For those that do require protection, there are measures that should be taken.
Apply the last application of fertilizer early enough in the season so that roses will have stopped putting out new growth before the first good frost. Leave the last blooms on the roses and allow them to form hips, which will also slow growth before winter.
Mound extra soil around a center of each rose bush--making a hill about 8 inches high--after frost but before the hard freezes.
Cut excessively long canes back to about 4 feet with sharp pruning shears at a 45-degree angle. Tie canes together with soft twine to protect from wind damage.
In extremely cold climates, mulch with straw or hay after the mound has frozen. In milder climates, pine needles and oak leaves can be used, but do not use leaves in regions where there is alternate freezing and thawing, as leaves will keep the canes too wet and promote canker fungi.
Place collars around roses to hold soil in place high up, around the stems. (Omit this step if you have poor drainage.)
Mound soil to cover roses completely and cover with a peach basket, placed upside down if temperatures drop extremely low. Another method in extremely cold climates is to dig a trench next to the roses, loosen the soil ball and tip it so the roses lay over into the trench, then cover the whole thing with soil.