Developers are responsible for all the server side magic. They do all the behind the scene technical things.
They have full power over the server as they run it. Developers have a blue name in the in-game chat.
Community Managers (as the name suggests) deal with the community. This can be anything from organising events to hunting hackers. They are cool people ready to help you.
They have power in numerous sectors such as the discord server
Chat moderators manage the chat to make sure The Law™ (the rules) is respected.
BATs play beatmaps in the ranking queue and decide whether they are good enough to be ranked or not.
The support team is here to help you with any issues you may face. They are accessable, nice people who enjoy working and helping people.
Here's a list of people who helped with Fumosu!