You have two choices --

1. If the database is in Archivelog mode and you have sufficient resources somewhere then restore the old backup and do a point-in-time recovery to just before the time you inserted the rows; Export the table and inport into original database.
2.If you are on 8i then use Log_Miner; It has undo commands for all those inserts.

ROWID may not work if there were subsequent deletes/inserts.

- Rajeev