Hi Ranjit,
I believe that Business and Template role types are currently not requestable through the User Access Request W/S. That is why you are able to submit the request via the front-end, but not via W/S. I had opened up a note with SAP on this in the past and the response was not supported and to submit as an enhancement request. I recall looking into the function module behind the W/S and seeing that it was not setup to handle role type = business / template.
I would be delighted if there was a way to request BRs via W/S so if there is a better answer to your question I hope we find it.