Well, the roll backs are caused by server crashes, which as far as we know are caused by hackers.

The roll back doesn't generally go to when it stopped responding, but to the start of the game, or when it last saved. Usually this is when you joined, but it's fairly random. You won't notice the 'unresponsiveness' for a bit after the server crashes, as the game hasn't been forced to send you new data yet. When it does, that's when everything stops responding.
