Following is the excerpt of online help for login module. In next version of CW, LMS 2.5, you are allowed to customize role. But unfortunately for now, there's no workaround.
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After you select and configure a login module, all authentication transactions are performed by that source. The CiscoWorks Server still determines user roles; therefore, all users must be in the local database of user IDs and passwords. Users who are authenticated by an alternative service and who are not in the local database are assigned to the same role as the guest user (by default, the Help Desk role). To assign a user to a different role, such as the System Admin role, you must configure the user locally.
