I always uncover my tender roses (zone 6-7) when the native trees start to leaf out. It seems late but they still bloom in June when I do it this way, and it seems to minimize the amount of spring kill.

Near the house and rated zone 4, you're probably fine now. My zone 3 & lower roses I never cover at all.

I would wait. I have mine mounded and covered in collars. As much as I want those ugly collars off, I would really wait until night temps are above freezing. Some of the hardy ones would probably be fine, but my thought is why risk it as this point? We have had the slowest spring in my memory here with new snow for the last 4 days. Waiting is hard...

And now for something completely different... I uncover mine pretty much as soon as I can. Well, the zone 3 and hardier roses I don't cover at all, it's the hybrid teas that I cover. This year I was uncovering them as the snow was melting off the mulch because it is such a late spring. They winterkill right to the ground most years anyway and the bits that remain alive above ground tend to put up weak growth. I planted them deeply and on a slant so there is lots of stem below the ground and it's this part of the plant I want to protect. When the soil warms, strong new sprouts emerge from below ground and grow very quickly. So I uncover early to give the ground a chance to thaw and warm so the roses can start putting up new shoots by mid-late May. If you don't use this planting method though then you are trying to protect the above-ground shoots and I'm out of my league on that one.

Oh forgot to mention, I prune dead canes when the new growth is about 4-6" long so it's easier to tell when something's really dead or not.

I have had a strange phenomenon many times where a protected cane remains green... doesn't sprout... all the others are growing and fully leafed out, the green cane still neither sprouts nor dies. It's odd. Sometimes it will eventually die but quite often it leafs out very, very slowly. I don't know what causes this.

Thanks for all the info! Guess I'll leave the peat mounds for awhile, probably won't hurt. Our last frost date is end of May but there can be frost any month. Hopefully it will soon warm up, this spring seems so slow.

I was anxious to uncover them as I think there were mice in the peat moss and I wondered if they had eaten them right down. Fortunately there are green canes but I'll wait to prune them.