Did you tell postfix to send all mail to rollernet.us? Please check there forum/docs, they should have examples!
Do you get login promt when you try to send mails? Elese you could add your local lan to the relaynetwork. If you dont get login promt you need to specify that authpam should be used for relaying.
Try to send with the webmail application too, check what mail.info/warn says in /var/log