now, the rollback segment have 3 states: online, offline, needs recovery.
Ok, so the 3'd state meens that the rollback segment 'X' had a transaction active in it (active= non commited). Now
you have 3 possibilities:
1. try to release the transaction active (it remains in the datadictionary), by relesing in the DBA_2PC_PENDING view or
2. if nr.1 don't work you will have in the data dictionary for ever the segment 'X' with the nees recovery status until you recreate the database.
3. (at your own risc):
IF nr.1 DON'T WORK.
update manualy undo$ table change the values status$ to online (numeric). Run catalog.sql & catproc.sql , then try keep offline by command and finaly drop.