RBAC is the new permission model in Exchange 2013. With RBAC, we don’t need to modify and manage access control lists (ACLs). It enables us to control at both broad and granular level, what administrator and end user can do. In Exchange 2013, RBAC now controls both the administrative tasks that can be performed and extent to which users can now administer their own mailbox and distribution groups.
Go through following link to understand more on the RBAC Permission in Exchange 2013
PowerShell to Customize RBAC Permission in Exchange 2013
Regards,
Krishna