BROSR is when you get to a landmark session number like session 70 but you're too busy to dm. So one of the players and occasional co-dm do it for you!
I didn't play or DM (obv) so I have no great comment on it. My thief Scamicus's downtime shenanigans and disinterest in cleansing the evil altar last time I was a PC was apparently the reason they had to take care of it this session.
So even when I'm not a PC they're still dancing to my tune. Good for them!