Answer: The answer to your question depends to some extent on what kinds of roses you are growing. The old fashioned shrub roses and modern landscaping roses do not need any special care beyond the suggested year round layer of mulch about three inches deep.
Hybrid tea roses considered hardy in your area might appreciate a bit of extra protection such as a mound of soil or extra mulch over the base of the canes, but in your area this should not be critically important because your winters are so mild. This extra layer of insulation would be put in place late in the season, once the ground has frozen. It would be removed in stages next spring.
Hybrid teas may also be trimmed back somewhat in the fall to keep the winter wind from whipping overly long canes and damaging them. They would then be pruned back harder in the spring to remove any winter damage and to optimize blooming.
Your local chapter of the American Rose Society may have more specific suggestions depending on the particular roses you are growing. You might also want to look at a book or two about roses, one I particularly like is Roses for Dummies by Lance Walheim, ISBN0-7645-5031-4. It includes useful diagrams and instructions for winter care, pruning, and so on.
Good luck with your roses!
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