Since the new honor system has been released I have seen more and more positive attitudes, or at least people not so quick to rage one another. I have a suggestion that would help the champion selection process.
Most friends I know that play have at least two roles they know how to play well...that being said, during champion selection, two people might call "adc" but one may have a lower ELO score and the person with higher ELO will not want to change their mind, I've seen it time and time again where they will both pick the same roles making it a troll game and not very fun from the start, which messes up any possibility of team chemistry.
My solution is similar to the same way we do the honor system now but with some added voting specificity with regards to champion roles . At the end of games, we should be able to elect one person as the "MVP" for their role, whether it be on my team or the enemy team...After so many awarded votes over a period of games, there should be an icon next to their name during champion selection. This notifies their team that this person is better suited for this role based on past MVP votes and exemplary track record. This will improve game play, for example: if I don't get my main role because someone has proven to be more successful at that role, I may be more apt to concede the role and choose another role. The icon(s) would indicate that they are better suited to serve the team in that role than I am. Gamers want their main role because they feel that they are the better suited to support the team in that capacity. They should be acknowledged for their performance within that role which should help alleviate trolling during role selection. It's true that people will continue to be stubborn about the role they want, but at least it has a chance to ease champion selection tension.