You are an innocent. Your goal is to survive. You don't know the roles of other players and the traitors are coming to get you, but don't randomly take out other players because you could be removing teammates. Sus out the other players, find clues to potential suspects, or team up with the detective to survive.
You are the detective. Assist the innocents in taking down the traitors. Utilize different gadgets like the binoculors to identify bodies from afar, the dna scanner to hunt down the killer, or others from your detective shop. Be careful though as all other players know who you are and some of them do not want you carying out your job.
You are a traitor. Your goal is to kill all other teams. You know who your traitor teammates are so try to discretely coordinate with them to take down the innocents. In addition to the normal pickups around the map, you also get access to various traps around the map and a wide array of traitor items in the shop.
You are the swapper. Your goal is the have another player kill you. Once they do you will smite them and assume the opposite team they were on. The traitors are the only team who know your true identity. It may be in your best intrest to work with the traitors, even though you may not know who they are, to get an innocent to kill you.
You are the marker. You goal is to mark 75% of the other players with your paintball gun. If successful you will win the round. Players who are marked by you are unable to damage you.
You are the infected. You goal if the infect the rest of the players. You are on your own and no other evil roles are lurking around, but when you kill another player, they are revived as a zombie and join your team.