I cut back my roses just as the leaf buds start to swell nicely. That makes it easier to see where to cut. This is my first year with a Knockout and I plan to just cut back some ratty looking stems and leave the rest.

Here's a link to a good publication on pruning roses.

Here is a link that might be useful: Rose pruning

Don't cut back roses just for the heck of it. Prune only if you know the rose requires pruning.

I wait until early spring when I can tell which canes, if any, are dead. These I cut back to living tissue or to the base, depending on the amount of dead cane.

You should not need to prune Knockouts or their relatives at all. In fact, the plants will have a nicer overall shape if you leave them alone. My Blushing KOs are leafy and have flowers to the ground every year and I don't cut anything except the reversions (and not even all of those).

if you don't prune knockouts they will eventually get way too tall and not have the shape you want. They should be trimmed like any other flowering shrub. I learned this from a very reliable source. If interested in the method go to the rose forum and read "Paul' Pruning Demo".

I am at the beach and we pruned last weekend like our local rose society suggested. I would wait at least another week for you. I know it is supposed to get down to the 30's a couple of nights this week down here. The last frost date for your area is a good guide line.