Absolutely! There are a couple ways you can select roundtrip flights.
First, you can select your traveler's preferred departure or return leg individually by hovering over the logo and clicking select. This will then display all legs that work with your selected flight. For example, by clicking "Select" on this departure flight will display connected return legs.
For maximum flexibility, you can run one-way flight searches. This will allow you to select two flights on different carriers. The easiest way to do this is to run a multi-city flight search from the TRAVO homepage and select flights individually.