Help configuring Roku device settings, using Roku OS features such as screen mirroring, adjusting display type and audio settings, using Guest Mode, and assistance with software updates.
Roku wireless speakers work with Roku TVs, not players. So it won't do anything with a Roku player of any model. For the highest quality sound, you should consider a full blown AVR with five speakers and a subwoofer. Naturally, that's going to cost more than even a high quality sound bar.
If you want true rear speakers, you'd have to find a soundbar that offers wireless speakers. Now, Roku themselves offer such a soundbar (Roku Smart Soundbar), and it has what amounts to an Ultra or Premiere built into it. It works with the Roku subwoofer and Roku wireless speakers. I've never seen nor heard one in use, so I can't offer any opinion of its sound quality. But almost any soundbar is going to sound much better than TV speakers. 
I'm sure there could be other options available as well, but you would still have to get a Roku player to connect to it (assuming the soundbar has HDMI inputs) or to the TV.
