If Auto Fill is Going to Stay
At least have the courtesy of deactivating it for players who aren't filled in champion select, but then suffer some other player dodging. You know, something along the lines of...
'Because you were given one of your preferred roles in the previous champion select in which a player failed to pick or ban a champion, you will still be guaranteed one of your preferred roles. Sorry for the inconvenience.'
The added apology is just a little something we, as humans, like to hear.