As long as you don't come back to the point of origin on one roundtrip using another roundtrip, it's end-on-end, not back-to-back.

"Point of origin" is usually where you live, but not necessarily. You could fly to somewhere (e.g., work) with a one way, and then fly home with a Saturday night stay at home, returning to work. Point of origin is work, not home, in that case.