Pretty sure he's on the test realm this week, so presumably next week.
At any rate, this has nothing to do with weekly free champions. Additionally, recently the new champs haven't been free their first week, so it'll probably be 2 MORE weeks before you can use garen.
My question: Whoever selects weekly free champions believes the five roles to be support, tank, mage/nuke, melee DPS, and ranged DPS. This is different from what the web site and in game champ filters suggest, which is support, tank, mage/nuke, fighter (DPS?), and assassin (ganker). And neither of these may be particular corresponding to what the community believes, which maybe puts carry in there and possibly disabler/stunner.
So why those five roles?