Just found this out tonight with my son, that "yes" you can turn off your soundbar. If you have the Roku App and your Android or Apple (not sure about other device models) is connected to your Soundbar look in the Upper Right Hand Corner on the digital remote on your screen and you'll see a little red power button icon. Same **bleep** icon that's on the actual remote! It will turn of the soundbar and disconnect from any wireless speakers.
Once you turn it off using this method though, you have to use the digital remote on your phone/tablet to turn it back on again. The physical remote will turn off your TV, but won't turn the Soundbar and the TV back on together - only the TV comes back on. My whole family loves this Soundbar and subwoofer; movies are awesome and Xbox is GREAT! Going to pick up the wireless rear speakers at some point.