Rank unlock: 30 games ATLEAST as each roll before you play ranked

I just played on a game with a dude that said he doesn't play supp and has few supp champs. Looking at his match history, it doesn't look like he sucks for his level. But how does he have over 100 win in ranked solo and never have been forced to supp on enough occasions to be half way decent? There should be a certain number of games you have to play in each role before unlocking Ranked mode. 30 in each would only be 150 by the time you were level 30. I think jungling is an acquired taste but I can do it. Supp seems like a standard position.