If roses are very shaggy, prune them ( thin them out and shorten scruffy twigs) in November to stop them being damaged by strong winter winds. Then in March you can reshape them if you want. Well, that's the classic advice. Some researchers once tried dividing a whole lot of roses in two, pruning half the classic way, the others with electric strimmer-type tools, and found eventually that the classically-pruned ones ended up with far fewer blooms. So do as you please.