You don't say what kind of roses you have, but here are some general guidelines. After the leaves have dropped rake up all the leaves and if affected with black spot, dispose of them in the trash. DO NOT compost them or you will reintroduce black spot spores when you spread the finished compost. There are several ways to help roses overwinter safely, but basically you need to protect the crown from freezing. After the plants have been exposed to a couple of weeks of temperatures below freezing they should be mulched with an organic material such as compost or bagged mulch. On grafted plants, it is important to cover the point of union. Extra soil can also be used to mound round the plants. The depth necessary depends upon the usual winter temperatures in your area. In cold parts of the mid-Atlantic region you may need to mound up to 10" to 12" round the crown of the plants to protect them. Another form of protection is to circle the bushes with a wire cage and fill the gap with dry leaves or straw. This is a good method in severe climates, but you need to be observant about rodents spending the winter dining on your roses.