Mass import OIA users into roles using web services

We are running Oracle Identity Analytics 11.1.1.5.2 and need to be able to perform a mass update of user to role assignment without overwriting the associated policies, both the roles and user records are already in the OIA database, however however role membership has not been populated.  Our thought is to use the "AssignUserToRole" module in the web services API to perform this update.  I just need to know how to do this?  Do I use a rbx and a csv file, or, use an xml file?  I'd like specifics on how and what steps to perform to get these roles populated with