Swapping a single roller on a door that's already down and de-tensioned isn't a hard job with the right stem puller, and plenty of Glen Ellyn homeowners handle it themselves on doors with sealed nylon rollers and modern track. Steel rollers on original 1972-era track are a different matter - the bearing races can be seized to the stem, and forcing them can bend the roller bracket, which turns a $15 part into a track repair.
If you're going to try it, do it with the door manually supported, the opener disconnected, and never with the spring under tension. If a roller's stuck and won't pull free with hand pressure after a few minutes of working it, that's the point to stop and call, not the point to reach for a bigger pry bar.