No ... I don't think you would need roles and permissions for the task project but since you were enthusiastic about the user and groups I thought I'd pass along a solution for a comprehensive (but external) user management system.

EDIT: I also should have mentioned that we're updating our original system to be compliant with the specification and open sourcing [1] the code that's not custom to our application.

[1] https://github.com/PennState/scim