Looking at Voice Procedure terms on Wikipedia has left me a bit confused:
Out — I have finished talking to you and do not expect a reply.
Over — I have finished talking and I am listening for your reply. Short for "Over to you."
I've certainly heard the phrase, "Roger, over and out," used in Hollywood and general pop culture, but given what I've read it seems like both terms contradict each other. You wouldn't be listening for a reply if you did not expect one.