Actually - I figured out a way to do it.
Hopefully this will help others.
Pick a song form the USB HD to play and go to the now playing screen.
Hit option - the menu pops up from the bottom and the shuffle /random choice is there for the using. Unfortunately, if you pick a specific song to play after shuffling, it turns off, but if you just want a general shuffle you can do that. It doesn't seem to work in playlists - but it does work for genre the same way.
Once it's chosen, hit the return button and the menu goes away.
Nice thing is that it can be controlled by the app at that point. Want to skip a song, just hit next and it pops up the next random track.
Hard to run it from the app to start without the tv on, but if one wants to play music randomly without the TV on, it continues to play after the TV is powered down.
Hopefully Oppo will update this functionality to include more places to use the random function in future firmware updates.