If you play a lot of League of Legends you've surely been matched into games where you haven't been able to play as the hero or class you wanted to as it didn't fit with the rest of the team composition.
Riot Games are now attempting to do something about this problem and in the near future they will release the new Team Builder queue in beta form. The idea is that this new queue will allow you to pick your preferred role/character and then the game will attempt to match you into a team where this role is missing.
Sounds like a great idea to us.