rollback

Hi everybody,
I was playing with psql and accidently deleted a couple of records from
my database. I am wondering if there is any way to restore them. I know
that in Oracle you can do 'rollback work' from SQLPlus interface and it
would rollback all the updates done to the database.
I am pretty sure that from now on I would try to revoke permissions to
delete anything from the database from users like myself. What is the
best way to do this?
thanks,

Oleg