Roku app is severely dated, its transcoding even when the setting of the server says not to do so.
Mp3 @ 320kbps are transcoded down to 128kbps which isn't needed as Roku can play@ 320kbps without issue.
Trancoding to and from and format has serious delays and dropout when streaming over the internet (lag time in the transcoder I believe).
Natively supported codecs are being transcoded and do not need to be in Roku app, actually causes degradation of video and audio when its not needed.
Video — H.264/AVC (.MKV, .MP4, .MOV), on Roku 4 only: H.265/HEVC (.MKV, .MP4, .MOV); VP9 (.MKV)
Audio – AAC (.MKV, .MP4, .MOV); MP3(.MP3, .MKV); WMA (.ASF, .WMA, .MKV), FLAC (.FLAC, .MKV), PCM (.WAV, .MKV, .MP4, .MOV), AC3/EAC3 (.MKV,.MP4. .MOV, .AC3), DTS (.MKV, .MP4, .MOV), ALAC (.MKV, .MP4, .MOV, .M4A)
These formats above do NOT need to be transcoded as they are natively supported.
the reliability, speed and efficiency of the roku app need improvement as it seems even 15mbps movies drop quite often even though my upstream is 25mbps and the receiver over the net is getting 43mbps downstream. However streaming with Emby Theater to the same person and connection has no issues.
Better handling of high bitrate encoded movies over the internet under Direct Play.
Lastly, being able to select ciphers for HTTPS is important and improving stability of the server app as a whole has others had similar complaints of instability.
BTW this is for the "Stable" of server and for the Roku app where it applies and is based on direct play.