Please always state explicitly the exact jboss version you are using. I'm guessing 2.4.4. I believe you can set up a JDBCDataSourceLoader that will be non-transactional. Sorry, I don't have an example.
Can't you make your procedure run within a transaction? Relying on transactions to get unique values usually doesn't work, usually using a sequence or generator or special table with auto-increment key works better and can be used in a transaction.