There isn't really a "correct" time. You have to go by your weather in any given year. Especially now days! A general rule of thumb is to start spring pruning when the forsythias start to bloom in your area. That usually means the ground has warmed up sufficiently for roots to start to grow and feed the plants and then they start to grow. If you don't have forsythia in your area go by what ever flowering shrub is the first to bloom around you. But you really can't kill a rose by pruning it unless it's grafted and you cut the graft off. I know some people who prune in the late winter before anything starts to grow and some who don't prune until late spring when they've already leafed out. You can take dead wood out anytime of year. You can also do a reprune later in the season after the first bloom. Don't worry about making mistakes. We all do all the time and the roses forgive us and grow anyway!

If you don't know what type of roses you have, prune lightly this year. Dead and damaged wood is always safe to remove. Aside from that, I'd do very little. Some types of roses only bloom on 'old wood' that was around last year, and some types bloom much better on old wood. Since they are usually hardier kinds, pruning out only dead wood works reasonably well.

Oh, thank you, Mad! I didn't even think about once bloomers!

As said, if you prune those deeply now you'll be cutting off all of this year's blooms. It might be a much better idea to wait until after the first bloom to prune deeply for shape and size this season. Then wait and see what happens. If your roses rebloom again this season then you'll know you can do your deep prune in the spring. If they don't rebloom you should only prune them after they bloom each season and then leave them alone until after the next season;s bloom is over.