Do you have any of the volume leveling/night mode options enabled?
Did you try any files with mp3 or AAC audio? Something that the Roku would decode itself?
Since the premier can't decode dolby, you'll need to feed it aac or some other audio codec it can decode internally.
Since it says NONE for audio when you click ok while the video is playing, it has decided that there is no audio track that it can play so it is only playing the video.
Setting the digital audio mode to PCM means that it will only pick audio that it can decode internally, which means no dolby,dd+,dts.
It will only be able to play AAC,wma,mp3,flac, etc.
The older Toshiba might be only able to take PCM for audio. You might need to make sure your serviio server is transcoding all audio to AAC.