When you attempt to add a role to a user or group in Exchange 2010 or 2013 the following error is displayed:
You don't have access to create, change, or remove the "<Role>" management role assignment. You must be assigned a delegating role assignment to the management role or its parent in the hierarchy without a scope restriction.
Run these commands in the Exchange Management Shell:
Add-pssnapin Microsoft* Install-CannedRbacRoles Install-CannedRbacRoleAssignments
Relaunch Exchange Management Shell