What are the biggest mistakes you see people make?

I've killed many roses and had few successes but I plan to keep trying. I've been growing roses for a few years now and the first two years had only one survivor, which was ultimately transplanted last year due to the deer eating it. Last year I bought 9 half alive bare root plants that were on clearance. All of them began sprouting but only 6 survived to be transplanted in the ground. One then got RRD and I removed it.

This year, all of them seemed to survive the winter and began sprouting. Now, the late spring frost has seemed to claim 2-3 of those. With that, I need advice on spring pruning. When do I prune? I've seen mixed reviews online and I don't know whether I'm part of the problem or not. I often start pruning when temperatures reach 80° and the plants start sprouting so that the black doesn't spread further down the canes. But this is in April and not after the last frost, I'm in Pennsylvania. Do I wait until the last frost to prune or wait until the plants wake up in warm weather?

So with all that, what are the biggest mistakes you see people make with roses, especially with roses that end up dead? Any advice helps.

This week I bought:

-Heirloom rose (it's purple)

-Oregold

-Double Delight

-Orange Glow Knock Out Rose

-Gold Glow (Not sure if this is right because there's red and orange on the petals emerging.)