The roles you can fulfill inside the gang are, in order of importance (AKA, the ones lower than you on the list you can give orders to), are...

1 - Mafia leader.
2 - Second hand.
3 - Corrupt Cop / Spy /Accountant / Trafficant / Hitman
4 - Brute.
4 - Henchmen.

Now here is a brief description of what these ranks do.

Mafia leader: Is the one who gives orders to everybody else. He lives a life of luxury and takes the most profit. He is almost immune to legal actions, and is most of the time he wily guarded.

Second hand: They are, as their name implies, the leader's second hand. They also tend to live a good life, but they also have plenty of work commanding lower ranks, specially henchmen. Usually a second hand specializes in one kind of job.

Corrupt cop: Pretty self explanatory. It's lower than the second hand in ranks, and it lives a pretty hard life, since he has to balance his actual job with his corrupt works.

Spy: Close to a corrupt cop, but he runs a lower risk of getting caught. However, when he is caught, he is pretty much going to end up dead.

Accountant: it's one of the most relaxed tasks in the mafia. You run their numbers (most of the time money) , but this also means you are highly dependable, so you better go your job well!

Trafficant: One of the most usual jobs, and the one most people choose. Your job is to trade all kinds of substances for money and viceversa. You also supply the bars and pubs.

Hitman: Not necessarily part of the gang (he will for this Roleplay though) , the hitman executes missions to, well, execute people. He can either do it silently or make it look like an accident. Depending on his success, he might be wealthy or not, but he also runs a very high risk/reward life.

Brute: this position. Is reserved for the strongest men and women of the mafia. Usually guarding secret pubs or protecting the higher ups. They are equipped with pretty powerfull weapons and are known to kill any people who threaten the safety of whoever or whatever they need to protect. They are not very high in the ranking list however, so don't expect much depencendy, or wealth.

Henchmen: This is the most dependable yet flexible rank. Everybody starts from somewhere, and that somewhere is here. Everybody bosses you around, and you have to follow orders for your own good. However, you can quickly rank up with earned respect. The henchmen can do all sorts of tasks, but most of the time they defend their leaders and help trafficants.