I don't think there is a simple "rollback" operation for tag creation already completed on the PI Data Archive. In the PI AF server, changes made to checked out elements are recorded in a sandbox, and only get committed to the database during a check in. However, on the other hand, once a command is initiated to create tags in the PI Data Archive, the tags are already created.
My suggestion would be to first check in your changes to the element (during element creation) to make sure all goes well. If there is no exception, you can then call AFDataReference.CreateConfig to create the PI tags. Treat them as separate operations so you can avoid tag creation if things go wrong during the AF element creation.
Thanks for the quick reply. You've confirmed what I thought. I have taken your suggestion and ensured that the tag creation only occurs when the element has been confirmed to be valid. In other words, I perform the tag creation immediately before the checkin.