Ranked Champ Select suggestion

Something has to be done about what champs can be picked for a certain role in ranked. I can care less about normals, but when it bleeds over into ranked, its frustratiing. There is nothing stopping trolls from declaring one champ like a blitz support and then picking and going ap Darius support and then they tell you: "nothing you can do about it". Can we get some kind of registration system where players enter 2-3 champions per role. I see no point playing adc in champ select and then having +100 champs available to pick when there are only a hand full of adcs out there. I actually had someone go Karthus adc and basically carry the other team with his shenanigans. this needs to stop