The CMDLET that get exchange server 2010 role assignment retrieves a list of the role assignments in the Exchange management server is:
Get-ManagementRoleAssignment
To add a member to a role group use the syntax:
Add-RoleGroupMember “GroupName” -Member “UserName”
Fill in the right group name under “GroupName” and the user you wish to add to this role group to “UserName”
The cmdlet to indicate if the user added to the group list is:
Get-RoleGroupMember “GroupName”
One of the frequent operations is adding a role to an administrator only and it can be done by this syntax:
New-ManagementRoleAssignment -User “User_Name” -Role “Role_Name”

Exchange 2010 gives us this flexibility to move between different role groups to create the exact operation we need.
For example: the organization has a Managers group which is a member of the “Special Operations” role group.
Say the “Special Operations” assigns the roles “send on behalf” and “Export Mailbox” roles.
Now the managers need a new role, for example: to watch the recipient members for a distribution group (which is blocked for all company).
To do this we’ll modify the role group “Special Operations” and add the “watch recipient members” role as follow:
New-ManagementRoleAssignment -Role “watch recipient members” -SecurityGroup “Special Operations”