Another test file for checking: TestFile2.mkv (dropbox link)
MediaInfo: TestFile2.txt (3.8 KB)
This file has very minimal delay compared to my previous test file.
I have a support ticket in with Roku and linked the two threads discussing this issue so providing details here may help Roku Support as well. I recommend anybody having the issue report it to Roku not just as a Plex issue but as a Roku Media Player issue since that’s their product to support in-house (though they did take my Plex info as well).