Just as the dust bins on a robot vacuum need to be emptied regularly, so do their brushes need to be cleaned. My Roomba (via the iRobot mobile app) bugs me every several cleanings or so to remove its roller and clean out the debris and hair that gets wrapped around its bristles. The procedure only takes a few minutes (the brushes on my particular vacuum are a snap to remove and replace), so it’s not a huge deal, but it’s a chore you don’t want to skip; if too much hair builds up in your robot, it could be permanently damaged.