I still disagree with the idea of a voting system to eliminate dodge penalties and here is why:
The entire idea about league of legends, which people always seem to forget is that this is a team game.
Sure, you may have that person in last pick who just refuses to fill, and will troll if he doesn't get his way. Shit happens sometimes, and you don't always get what you want. Do you want to know how people who are now pro's handle people like that? Simple: instead of arguing, they fill into a role.
That's what you need to do. Instead of constantly complaining about trolls, or instead of constantly complaining that you have that one person on your team that loses you the game, you have to figure out how to perform to mitigate for that lack of teamwork. YOU have to be the person that steps up.
And lets say that you're not in the middle of this issue, but instead are finding someone that doesn't want to fill for a role that somebody other than you is taking: You need to explain to them what will happen if they troll. I've found that saying something like this usually works:
Hey man, I know that this guy took the role you wanted, and I totally feel you man, we've all been in the position where we don't get what we want in this game. Even then,if you were to pick for the role that's already taken anyway, not only would you have a horrible match to deal with, but you would also be ruining the game for three other people that have done nothing to harm you. I ask you to fill, just this once. All I'm asking is for you to fill for about forty minutes, there will be other games dude, you'll have your chance to get your role in other games. Let's just try to make do with what we've got and we'll go from there. :)
If the player sees your side of the view, more often than not he will fill, and if he specifically says "I just really don't want to support" or "I don't want to jungle, I'm bad at it", you should be willing to say "that's cool man, why don't you take my role and I'll take support?". THAT'S how you work as a TEAM.
tl;dr: If someone on your team doesn't want to work with the team, it's your job to step up, not riots.