Can’t play any HD movies/TV shows on Roku, but I can play them on my Vizio TV.
What kind of issues do you experience?
Are the files failing to play entirely or are there some hiccups / buffering / … (either in general or at specific points)?
What information is showing in the “now playing” tile for that playback on the Plex server dashboard? — e.g. is the connection from your Roku listed as local, remote or indirect? Any transcoding?

https://support.plex.tv/articles/200871837-status-and-dashboard/
How can I see it playing when it just won’t play. Everything is local.
Can you explain why they work before the 1.42.2.10156 update?
Well, that’s what I’m trying to clarify.
Are you getting an error message or is the video just buffering endlessly?
If I can’t play it. It means that there is an error.
“Playback Error: Playback has stopped due to multiple playback errors. Please check your connection and try again”