I think it's taken on a non-technical meaning as well.
On a slow night, I've had a controller just chat to pass the time, saying something like, "I've got family near Copperhill. That's beautiful country!"
To which I might reply, "Roger that!"
Appropriate usage? Who cares - it gets a message of confirmation across.
BTW, before I was a pilot I was interested in aviation, and in a movie when they said, "Roger. Wilco. Over and Out", I understood that to mean...
I understand.
I will comply.
End of transmission.
End of exchange.