"Our tickets are returns" would be natural English and I think a correct translation. Strangely I think "Our tickets are round trip" could be OK but would probably be used about more exotic journeys - transatlantic sea crossings, special air journeys etc, I do agree not typical at the train station!
"Ours are return tickets" or "Our tickets are returns" would be a more natural translation. Normally, in England, we would say "We have return tickets".
Agree. Wrote "our tickets are return tickets" and it was rejected (2017 April 21st)
The audio REALLY sounds like she says "de dus-intors" instead of just "dus-intors".