Planting roses is fairly simple gardening stuff. The first thing is to never let the rose roots dry out. If you do, the rose will either perform poorly the first year or simply die. It does help to soak the roots in warm water for an hour before you plant if you’ve purchased the rose as a bare-root plant. Container grown plants do not have to be soaked.
Always did a dollar sized hole for a 25-cent plant. The bigger the hole, the looser the soil will be and the easier those tiny feeder roots will grow quickly. I can’t emphasize this enough. And never, ever (with a bare root plant) cut off healthy roots. You can remove broken roots but leave every healthy one that’s on the plant. They’re your ticket to early blooms.
When you back-fill the planting hole, I always add one shovel of peat and one shovel of compost for every three shovels of soil. This gives the rose some quick nourishment and makes a wonderful soil for expansion. The only exception to this is if you’re planting in a clay soil and then I only add the compost. I do not add the peat as I want the rose roots to grow out into the soil that surrounds the planting hole. They might establish faster in peat-amended soil but they’ll grow better and survive longer in compost-amended soil.