We have just released a hotfix related to filtering champions in your summoner profile and then joining a Ranked Game. Previously, if you filtered to only view certain champions (such as "tanks") this filter remained when you joined champion select. This has been fixed for Ranked Games.
While we are still researching the issue to fix it with Normal Games, please be advised: If you join queue, then filter your champions in your summoner profile, and then join champion select without removing the filter, you will be limited to choosing only those champions. Please turn off champion filters before selecting to "Join Champion Select" while playing Normal Games.