How to let people assign their own role?

[Hunter Lyons]

Is there any plugin or way I can allow people to assign themselves secondary roles? I'd like to be able to just have a link that people can click, which would assign them x y or z secondary role depending on what role ID or what have you that I put, but  I only want certain roles to be assignable like this for security purposes.

The reason is that I run a Gaming Club at my University, and we have tons of communities (sub-clubs that focus on specific genres), because we have 400+ members. I'm designing our home page (pictured below) and want to put links that people can click to join specific communities (that is, links that assign them x y or z role for that community).

[kmk]

By default the user sign up to a member group, at the sametime let the user request to join to others communities or groups, but the request should be sent to related community moderators for aprouval. 

I need this feature too. 

[Adriano Faria]

If by roles you mean groups then you have this plugin:

 

[bfarber]

Frankly, I would suggest looking at leveraging Clubs instead of secondary groups for this purpose. You can let users sign up for clubs (which will give them access to the club contents) without messing around with group memberships.