I live in Annapolis, Maryland. I planted a knockout rose about six or seven years ago in full sun. It blooms really well in the spring and fall but the blossoms don't last in full sun on a day over 80°. I cut one branch back to about 3 feet tall and it is now blooming a red rose. Also, my knockout rose is at least 6 feet tall, which is taller than it said in this article. I read on this website you can cut them back to only 3 to 18 inches or so above the ground, but I wonder if that would go back too far and make all my pink roses turn red. I was looking for information on how far I was allowed to cut it back so that I could make it small enough to transplant to a morning sun/afternoon shade area. How large a root ball should I dig up to transplant?
Rosebushes average growth habit is usually what is referenced in articles and in the information given on any rosebush. In some climatic conditions the rosebushes will either be shorter or taller depending on those conditions. In harsh winter climates many rosebushes canes die back to where the canes need to be pruned back quite a bit, sometimes to the 3 inch point above the ground. I would shape prune your rosebushes to the shape that you need them to be and then do a consistent maintenance pruning to keep them within the acceptable shape, this will help train the rosebushes. I would recommend digging up an 18 to 20 inch diameter area and at least that deep of a root ball for transplanting. Here is a link to an article for you as well: https://www.gardeningknowhow.com/ornamental/flowers/roses/transplanting-roses.htm