Role-based access control, or RBAC, is designed to limit the capabilities of superuser. Superuser, the root user, has access to every resource in the system. With RBAC, you can replace root with a set of roles with discrete powers. For example, you can set up one role to handle user account creation, and another role to handle system file modification. When you have established a role to handle a function or set of functions, you can remove those functions from root's capabilities.
Each role requires that a known user log in with their user name and password. After logging in, the user then assumes the role with a specific role password. As a consequence, someone who learns the root password has limited ability to damage your system. For more on RBAC, see Role-Based Access Control (Overview).