Find Rollback transaction in oracle

Rollback transaction Status:

select usn, state, undoblockstotal "Total", undoblocksdone "Done", undoblockstotal-undoblocksdone "ToDo",
decode(cputime,0,'unknown',sysdate+(((undoblockstotal-undoblocksdone) / (undoblocksdone / cputime)) / 86400)) "Estimated time to complete"
from v$fast_start_transactions;

Find rollback session details:

select s.sid, s.username, t.xidusn, t.used_urec, t.used_ublk
from gv$session s, gv$transaction t
where s.saddr=t.ses_addr
order by 2;