The general rule is to prune a rose bush just prior to the plant's breaking dormancy after the final frost of the season. In warmer climates this is as early as January, and in colder areas, it can be as late as April. There is an exception with old roses, which bear flowers on the previous year's wood. These are pruned immediately after they bloom.
Regardless of the timing, basic rose pruning is done to maintain plant health and involves the 3 D's: removing dead leaves or wood, cutting off diseased parts and eliminating damaged branches. In cold climates, pruning is often reduced to cutting back wood killed during the winter, typically brown or black, by removing entirely any dead or diseased stems. Old and twisted branches are removed as well as suckers at the plant base. Pruning cuts are always made at a 45-degree angle directly above a healthy bud to stimulate plant growth and provide energy to the specific canes that are to bloom. Removal of grass and leaves that remain around the base of the rose bush discourages insects and diseases.
In warmer areas, pruning is done on one of three levels, depending on purpose. Severe pruning to three or four canes, each 6 to 8 inches in height, produces fewer blooms that are larger. Moderately pruning a rose bush to five to 12 canes that are an 18- to 24-inch height increases the size of the rose bush, and light pruning, with less than one-third of the plant removed, increases the number of flowers produced on short stems.