It depends on where you are, but I do mine in late Jan/early Feb.
If you are in the high desert you probably want to wait a little later.

The latest research shows that the best time to prune roses in California is during the summer growing season. Contrary to conventional wisdom and popular belief.

Roses should be pruned as you would any flowering shrub. After each flush of bloom, prune out the spent flowering canes and skinny canes back to where they're larger than a finger.

If you do this after each flush of bloom, you won't have a bunch of scraggly canes that need serious doctoring come winter.

And we don't prune back roses, at any time, to short nubbins. That's a practice that evolved back east and in the midwest where winter cold and snows forced rose gardeners to cut their roses back hard so that they could cover them with piles of mulch and burlap and god-knows-what-all-else. We don't need to do that. Again, prune roses just back to good finger-size canes, usually pruning roses no more than 1/3 to 1/2 depending on their vigor. We should have BIG rose BUSHES, just as we have big BUSHES.

Also, the fact is that in most of California, our roses don't actually go fully dormant. We read about this in gardening magazines every year -- "ways to make your roses go dormant" (cut off water, fertilizer, leave the hips on, etc.). If you know about the genetics of modern roses, you know that one of the primary parents is Rosa chinensis. And R. chinensis is a subtropical to tropical species that is pretty much evergreen in the wild.

But there's a reality here: you've asked your question because you probably haven't done your summer pruning as noted above and you're ready to go in and do some winter "dormant" pruning of all that scraggliness. If you can't find a good calendar for pruning for your area (it varies), simply watch your rose bushes. As soon as you see even the slightest bit of bud swelling and/or new growth, have at it. Just be careful.

Joe

I prune mine in January in the SF Bay area, basically just to force them into dormancy during the "normally" wet times of the year.

I also "whack" them back during the regular season as Joe suggests.
But I've found that when I strip the old leaves and prune them in Jan., and then spray them with sulfur, I get less fungal diseases, esp. if we have a wet spring.

I think roses are forgiving no matter when you prune them.

wanda

While I haven't checked everyday, I don't think there is a day in the year when my roses do not have some new growth. We have had several days already in the 26 degree range, and I still have roses in bloom, growing new shoots to feed the deer through the winter. I do normally prune them back about the end of January, blooming or not. I love the clean smell of sulfur and give them a good dose at that time. Al

Shipments of Roses are coming into the Nursery rather fast now packed in sawdust. When we get them we prune again and take out all the little twigs, even cut off some of the top larger canes we shape them again before potting. We may even cut out a cane, if it looks diseased, or damaged. Leaving three strong, canes, we want them ready for Mothers Day and the end of May, I live in a warm area where we get an early spring. They are potted into 1-5 gal. containers upon arrival with the proper soil mix the roots may be trimed as well. We don't water until we see new growth. Pruning is a on going job, the dead rose heads are taken off daily so encourage new buds. I help with the dead headinig of old flowes. Norma

Norma's nursery is certainly treating bareroot roses as they should be treated by anyone having the chance to buy them "bareroot". Except of course there is no point of potting up roses that can be planted directly in the garden saving the purchase of a gallon or five gallons of potting soil that falls off the roots when the rose is planted in the garden. A ten dollar bareroot rose becomes a thirty dollar five gallon potted rose, indicating you have paid twenty dollars for five gallons of potting soil. A might expensive for potting soil. The experienced gardener knows when bareroots are due in the nursery and is disappointed when the retail nursery declines to sell them "bareroot". Al

I would agree with Wanda that whatever other pruning I do through the year, a Jan pruning and stripping of ALL the leaves, my roses look much better through the spring and summer.

I should add, that as Joe suggests, I prune my rose bushes by no more than 1/3 to 1/2. I also clean out center growth to open up air flow and anything smaller than a pencil, and crossed/damaged branches.

On the climbers, I don't prune the central long canes, but only the side growth and down to 1/3 as with climbers that bloom on the side growth, you will get more flowers.

wanda
who really does'nt like the smell of sulfur, but likes roses without black spot and rust.

I have 3 rules I follow:

I do not prune roses to the ground or just leaving a few canes. I just shape lighly and deahead all year long.

I do major pruning in August as the heat seems to cause the blooming to pause. I remove dead canes, crossing canes, branches smaller than a pencil. This promotes new growth which is what roses need to push blooms. You would not do this in northern climes as you do not want to encourage growth heading into winter, which we do not really have. If the leaves look tired or beat up, I strip the bush. Then I am assured of having roses right through the winter. In fact, the rose parade in Pasadena is a tradition to celebrate this very fact.

Keep in mind, the above is for Hybrid Teas. The majority of mine are shrub roses that just need a shaping and cleaning up. Actually, these roses don't have to be pruned at all if you don't want to. I just clean and shape.