Riot, do something to trolls who take others' lane.
The question is simple: What should we do if someone, say, who's autofilled as sup insists on going jg, takes JG CS, mess up the whole team's progress, lose and say "GG!" after the game and leave? Will I report him? Yes. But does that change the fact I lost LP, demoted, or a promotion? No. Riot has no means to stop these trolls before the game starts. Other nice players either have to cave in to these trolls demands, dodge the queue and face 5 min penalty, or worst, just go with it because "chill dude" morons who enable these trolls. Nobody wants to waste 30-45 min with jerks who whine about being autofilled and steal CS from other roles.
What are you going to do about it, Riot? Are you going to let the troll take advantage of other players? Clearly reporting doesn't stop them.