Roku players only support a couple of audio codecs, most commonly used is AAC and AC3. And of course your TV has to support both or you don't get sound. AC3 is no problem, since that's the TV broadcast standard in North America, and probably most of the world. See
this page for the exact specifications of supported media. Notice that the container matters as well.
Dan
Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.