As topic title. During either setup, or name selection phase (an extra dropdown box would make sense here), a player can choose their preferred Alignment (Town/Mafia/Neutral), and/or roletype (power/support, basic/advanced).
I believe this will increase the enjoyment of mafia games for players, as they will have some influence on the RNG on the type of role they will get. Depending on the players mood when the game is starting, they could want to play different or specific styles. This could also reduce the amount of players leaving a game when they get a role they really don't like.
Personally, I think the survivor is a really cool role but I've seen plenty of people leave straight off the bat or complain when they get it. That's the sort of behavior that has inspired me to make this suggestion. Don't just assume everyone will all pile on the mafia or neutral sides.