There is a status column that describes what state the rollback segment is currently in.
Normal states are either online or offline.
A rollback segment falls into this status of needs recovery whenever Oracle tries to roll back an uncommitted transaction in its transaction table and fails. If for whatever reason, that data block is unavailable, the undo cannot be applied. The result is a 'corrupted' rollback segment with the status of needs recovery. 2-If the object the datablock belongs to is corrupted. 3-If the datablock that is corrupt is actually in the rollback segment itself rather than the object.