Certified GKH Gardening Expert
Since the rose is root bound, go ahead and plant it right away into the ground. Water the rosebush with some water that has a product called Super Thrive in it the day before the transplant. Then after transplanted, water it with some water that has both Super Thrive and Root Stimulator mixed into the water. This will help it with any shock or stress it may encounter. Try to lightly break up the roots a bit to get them out of the shape of the pot. You will break some but if not loosened up a bit, they will stay in the shape of the pot.
Prune off all buds and blooms before transplanting, it is good to prune the rose canes down a bit prior to transplanting as well. Doing so makes the bush easier to work with. If it does start to form new buds, prune them off. You want the rosebush to focus on its root system and building up energy to go through its dormant period. Be sure to give the bush some water all through the winter season, especially so if you do not get much moisture naturally. Its root system will not be well established thus having soils moisture close by is highly important.