You can play or shuffle directly from an Artists screen or Album screen (there is a button on the left hand side). You can also shuffle/unshuffle the music from the Now Playing screen while your music is playing. We are looking to further improve and add features, so it's definitely not complete. For example, you may want to shuffle the entire music section. While that is not possible from the Roku interface yet, you can use Plex Companion and cast the entire library, shuffled, to your Roku.
Search is not available yet, but is on the list.
Something I've been hoping for is better ability to shuffle music either in an entire library or folder. I can contort the existing app to do this by doing a blank search and then play/shuffle the results, but I don't see a way with the new app, and would like it to be a simple menu option.
also, did I miss how to search within my server or library? Can;t find that at all.