Now you can run the Plex app in Android or on Roku without a media server and you don't even need to link it to an account. But Plex gives you a better user experience if linked to a Plex account.
Since Plex started offering free movies, they are becoming more like a stand alone streaming channel. Versus the clunky media server software running on a PC while the channel was used.
So if you have not tried adding the Plex channel lately, to see some cool movies, and channels it offers from their standalone app. Be sure to add it to your favorite device and give the Plex app a try.
Here is how to add a tool to Plex Server to watch IPTV Streams on Roku