I'm done with this "hey can you play something else so I can play [whatever]?" every single game. Every game one of my team mates says this, then proceeds to do awful and basically lose us the game because they have no clue what they're doing.
Just give people the role they queue for, it's that simple. If they want to play the most popular roles, then they will have to sit in a longer queue. But, guess what? It will be a higher quality game for them and everyone else because they will get a roll that they know how to play instead of troll and feed.