Update New-ManagementRoleAssignment.md

Added on-prem only and Unscoped Role Management role only to UnScopedTopLevel parameter per Issue #1387

Author: chrisda

exchange/exchange-ps/exchange/role-based-access-control/New-ManagementRoleAssignment.md

@@ -351,13 +351,15 @@ Accept wildcard characters: False
 ```
 
 ### -Force
+This parameter is available only in the cloud-based service.
+
 The Force switch specifies whether to suppress warning or confirmation messages. You can use this switch to run tasks programmatically where prompting for administrative input is inappropriate. You don't need to specify a value with this switch.
 
 ```yaml
 Type: SwitchParameter
 Parameter Sets: (All)
 Aliases:
-Applicable: Exchange Server 2010, Exchange Server 2013, Exchange Server 2016, Exchange Online, Exchange Online Protection
+Applicable: Exchange Online, Exchange Online Protection
 Required: False
 Position: Named
 Default value: None
@@ -398,7 +400,11 @@ Accept wildcard characters: False
 ```
 
 ### -UnScopedTopLevel
-The UnScopedTopLevel switch specifies that the role provided with the Role parameter is an unscoped top level management role. You can only create a role assignment using the UnScopedTopLevel switch if the role specified using the Role parameter is an unscoped top level role.
+This parameter is available on in on-premises Exchange.
+
+By default, this parameter is only available in the UnScoped Role Management role, and that role isn't assigned to any role groups. To use this parameter, you need to add the UnScoped Role Management role to a role group (for example, to the Organization Management role group). For more information, see the "Add a role to a role group" section in Manage role groups (https://technet.microsoft.com/library/jj657480.aspx).
+
+The UnScopedTopLevel switch specifies that the role provided with the Role parameter is an unscoped top level management role. You don't need to specify a value with this switch.
 
 ```yaml
 Type: SwitchParameter