Not sure when this happened... but I believe the Roku Plex app had an update somewhere in February. Since then, all of my Rokus have had issues default loading a lot of files. In this most recent case (logs attached) it was a Plex DVR'd file from a 480i channel.
The only way I can get these files to play is to load them with Direct Play and Direct Stream disabled, which I believe forces a transcode.
Logs and file XML attached. I can reproduce the issue at any time, with several files.
EDIT: To clarify, the file loads to 99% and then I get an unable to load error. Also, my Premiere seems to be handling them fine. The Roku TV and the Roku Express are struggling.