Roku players and TVs can steam many file formats and the Plex Media server can stream many as well. The Plex server software includes a built-in transcoder which can convert files “on the fly” as they are streaming to a device. As you might expect, transcoding takes CPU cycles and can degrade your streaming in the event you stream more than one file at once. To reduce processor load you can store your files in a preferred format for streaming with Plex. You can read more about preferred formats for Roku devices in the Reference section.

While Plex and Roku are perfectly capable of streaming 4K video, there is considerable overhead (CPU, disk and network bandwidth) in doing so. With this in mind, I tend to keep a small library of 4K content and duplicate that content in 1080p for streaming to mobile or lower resolution displays.

screen HandBrakeCLI --preset "H.265 MKV 1080p30" --encoder x265 -i Movie-File-4K.mkv -o Movie-File-1080.mkv

References

• Roku Streaming Specifications