as always I like to know how things are progressing especially when they are running long. This is also the case with ROLLBACK.
Here is a statement that helped me:
SELECT s.username, s.sid, s.serial#, t.used_ublk, t.used_urec, rs.segment_name, r.rssize, r.status FROM v$transaction t, v$session s, v$rollstat r, dba_rollback_segs rs WHERE s.saddr = t.ses_addr AND t.xidusn = r.usn AND rs.segment_id = t.xidusn ORDER BY t.used_ublk DESC /
I am interested if there are better options.