I live in N. Utah and am new to gardening. We have several well established rose bushes that have been neglected by previous tenants. I pruned somewhat in spring (March). My question is when do I prune them for winter and how severely can I prune?
In general I wouldn't recommend pruning roses in the fall in a colder climate zone. You risk promoting disease and interrupting the dormancy cycle of the rose bushes. Outside of general cleanup (removing dead and diseased canes, deadheading, etc.) which can be done at any time, I would recommend only pruning in the spring, just before bud break on most roses, or just after blooming on certain hybrid teas that bloom on old wood.
That said, roses are pretty tough once established and will probably survive most emergency measures undertaken when they are dormant.
Roses in colder climates like to be "tucked in for their winter nap" Give them about 6-8 inches of mulch. The rugosas which do not like being fussed over get a light blanket of 1-2 inches,which I think that I do more for me than them. I'm up here in northwestern Mass