If I travel outside the Stases, and I'm not allowed to came back, can I still purchase a round trip?

Answer 1

You can....but you need to check with your airline. To visit the foreign country, you may need to purchase or register for a visa. Check around your city to see if the foreign country has an embassy here. The below site may help because they are the Security bureau in charge of screening passengers in the U.S.

Referring to your question, there is no point in purchasing round trip if you know you are not going to come back. Just purchase a one-way...

Answer 2

there are a few advantages of purchasing a roundtrip ticket; its less expensive vs just a one way tkt; u can and might leave the return as an "open tkt" and use it for a later return date; granted they might be just a bit pricier but that is what u paid for; the time and flexibility. like the above answer mentioned, along with the obtained visa, depending on which country ur visitng, some countries actually want the arriving airline to verify passenger to required to have return and onward tkt to show they have means to leave the visited country. an online websit might not informed u but if u buy thru a travel agent they will def shed some light and be helpfull in this area.