You can check the LeaverBuster FAQ page anytime you have any questions about how it works. Basically, if you've been punished by LeaverBuster, you are placed into what they call Low Priority Queue. It begins with a 5 minute wait prior to entering the queue, then 10 minutes, then 20 minutes. Each time, you have to play 5 games to be taken out of the Low Priority Queue, but if you continue to afk/leave after the 20 minute LPQ timer, your account may be subject to banning.
The LeaverBuster is based on a pattern of consistently leaving/afking, which is why players who only leave games extremely seldomly are less likely to face punishment. The more games you play without having any disconnects, the better standing your account will be in, and the less likely you will be to face further punishment. Best of luck in the future, and hopefully your roommate stays away from that router!