Creating a Last Updated trigger

On a particular table, I would like to have a column called "DATE_UPDATED" that notes the last time an entry was entered/modified.  The trigger before is for a BEFORE versus an AFTER which prompts a question: If I am in a package and modify a record in the table (which causes the Trigger to fire) but I then roll back, what will the updated value be? The old value or the new one that the trigger caused? Is there a way to make an AFTER trigger? It keep giving me an error if I try.

create or replace trigger trigger_request_lastUpdated before insert or update
on REQUEST
for each row
begin

        :NEW.date_updated := SYSDATE;
END;
/ Received on Wed Jul 24 2002 - 17:13:37 CDT