Current rollback segment

Someone munching up all of your rollback ? The following script may be of assistance, it will show the rollback segment for a known SID.

select r.name 
from v$rollname r, v$session s, v$lock l
where r.usn = trunc(l.id1/65536)
  and l.type = 'TX'
  and l.sid = s.sid
  and s.sid = &known_sid
/