Whenever I cut back branches bigger than 1/4 inch, I use pruning paint on the cut to seal it. Pruning paint is not recommended much anymore but when I used to cut back my thicker branches, I had a lot of problems with die back. I called the rose hot line and they recommended I use the pruning paint. I found that you also have to make sure your pruning tools are sharp and clean. You should disinfect your tools after every cut since roses are very susceptible to fungal and bacterial infections. In my humid and wet climate, it was hard for me to keep the fresh cuts dry enough (it rains almost every night in Nov-May) overnight, much less for a few days. The pruning paint seals the larger cuts and I have a lot less die back. Some of my roses have been in the ground since 1992. I used to have to replace some of the roses every couple of years because I kept losing main stems. I just replaced a couple of roses this year, but the roses before then had been in place for close to twenty years. Olympiad, one of my new roses, may not be a keeper since it is more susceptible to black spot and I accidentally bought two of them. The other is in a pot.