intentional trolls allowed in plat elo

Just had two ranked games in a row in which one player in each game decided, from champ select screen, to simply troll the game. First one was a blitz support who didn't get the role he wanted, so he sat afk at bot tower until he was killed, and then repeated that 9 times. Second game, a player simply said he wanted to make us lose for fun, picked soraka after we already had a support, and he has cleanse and smite or something. Both of them were unbelievably toxic and acted as though they played like that all the time. I don't understand how people like this are still allowed and not detected or dealt with at all? I think there should be positions are Riot whose job is simply to monitor random games and chats in game and in champ select, and simply timeout people like this, just like people in twitch chat who are muted or banned for some amounts of time. Rito needs game mods.