Southwest issues awards as a pair of one-way award tickets (ie, they don't restrict them to round trip usage), although both one-way trips have to be booked and flown within a year of the issuance of the award tickets. Southwest works on credits, not miles. You need 16 credits for one of these "round trip" awards, and those 16 credits are generally much easier to earn than the 25000 miles that most airlines charge for a RESTRICTED* round trip; for example, using some credit cards you only need the amount of spending that would earn you 12000 to 20000 miles on other airlines to earn 16 Southwest credits.

*That's another important point: Other than a handful of blackout dates a year, all Southwest award tickets are UNRESTRICTED, usable as long as there is ONE SEAT left on the plane.

But there's no way you can request a single one-way ticket for 8 credits (these "round trip" tickets, which as I said are actually pairs of one-way tickets, are sent to you automatically as soon as get 16 credits).

OTOH, Southewest award tickets are transferrable, so if you can find someone who can use the other one-way ticket, that would be another way to not "waste" the other half of the pair.