"Biletul meu este dus-întors."

Should this be a return ticket rather than round trip? Does the ticket take one in a loop back to one's destination in one go? If so it is round trip.

I agree with Coriander. A round trip is exactly that (eg, Bucharest, Sibiu, Brasov, Bucharest), not a return. However, thank you so much, Duolingo, I no longer have to write "two-way"!