I used to be able to scan my library for changes from the Roku app, and it appears this feature has been removed. I would like to say I very much preferred the app the way it was before this current iteration.
I would pay a great deal to have the old version back. Functionality is worse, tasks take more clicks, its laggy, buggy. I would also welcome a refund on my plex pass. Unfortunately I have started exploring alternatives to Plex. That is not something I enjoy saying and wish it were not the case. Whatever changed at plex, please take a look at things.