Hi Thomas!
My thoughts:
1) It's only necessary insofar as you care to cultivate valuable relationships between your people. One might run a shared workspace with no effort to build community and call it coworking, and maybe some community will emerge on its own. I don't consider this to be in the spirit of the movement.
I'll add that the "role" can take many forms; it need not be an individual with a job title. Ideally, everyone in the community plays a role, with leadership creating the circumstances that encourage and empower everyone to do that.
2) Responsibilities:
1. Ensure the space is a safe space for everyone.
2. Be nice and encourage others to do the same.
3. Look for opportunities to introduce, empower, encourage, celebrate, and give permission.
4. Help people clear up any issues that arise, ideally by showing them how to resolve things themselves like grown-ups.
5. Not become an individual linchpin of the community, such that it would be seriously injured if you leave.
3) Tasks:
+ Talk to people
+ Develop programs
+ Work with others to develop their programs
+ Ensure stories are getting told, online and offline
+ Assist with day-to-day operations
Off the top of my head!
Tony