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.
"Round-trip ticket" means that the same as "return ticket" even if you find the latter more logical. Both terms should be accepted. The Romanian is similar to the French: "aller-retour."
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"!