on Drupal 7 how I can give to the "special" role the possibility to manage roles of other users (add a role to a user, remove, add more than a role, etc.), but not the possibility to manage all user permissions?
Use the role delegation module
This module allows site administrators to grant some roles the authority to assign selected roles to users, without them needing the administer permissions permission.
For each role, Role Delegation provides a new assign ROLE role permission to allow the assignment of that role.