It's a bit confusing, but if it is about subtitles for videos/programs - it is not a font issue; it is a subtitle file issue.
The Roku player doesn't translate subtitles or audio.
The developer must add subtitle files for every language they want to display/ make available.
When a subtitle is added to a video/program, you can find all available options in the language selector. If it is not there, it wasn't added.
There is always the option to contact the channel owner and ask for subtitles in the language you are looking for.
Have fun!
