How to set permissions to a particular role?
Looks like you should try the Role Delegation module. Some details from its project page:

... allows site administrators to grant specific 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.
The module also adds an assign all roles permission. Enabling this permission for a role is a convenient way to allow the assignment of any other role without having to check all the assign ROLE role permissions on the permissions page.