We aren’t intentionally doing something that causes a rollback. There are a few bugs which can cause the servers to get confused as to what the most recent data is and a newer version of your characters gets overwritten with an “older” one. Technically it is a newer one but it’s not the most recent one you were in control of. It’s a long story but we are working on it and we have some solutions in the pipe that are being validated. There is no way you can tell if it’s going to happen as a player and there is no specific behavior that I can recommend avoiding in order to reduce your chances of experiencing one.
We know all too well how frustrating this is and it is a top priority to fix. This is one of those things that must be fixed.