What you are trying to do is against Roller Network's Backscatter Prevention Policy:http://www.rollernet.us/policy/backscat ... ntion.html
Quote: "If our mail servers accepted a message on behalf of your mail server, then you must accept the message, regardless of actual intent or content."
You can probably configure your own mail server to first accept all messages from RollerNet servers then generate non-delivery messages to be sent as separate emails. But again, sending those non-delivery messages through RollerNet servers will be in violation of the above policy.
Sending non-delivery messages back to the original sender is a bad practice. Those should be generated by a sending server.