From week to week i need to re-link my ROKU to my PLEX account. Same ROKU, same TV, same location. The app shows my server unavailable when the server in my house is running. Re-Link works but doesn't last more than a week between uses.
I can't say I've seen the same behavior. I usually only use Plex when I'm traveling, so it might be several weeks minimum before I use Plex on that particular Roku player (my Stick is in my suitcase and is only used when traveling). On rare occasions I've had to re-authenticate to my Plex server from any device, but at times it even happens with the web page. I think it's something within the Plex channel, and possibly even within the Plex server software that forces a requirement to log back in. The best place to ask this question is on the Plex forum, not here. https://forums.plex.tv/