The problem is that the blue-tooth firmware that is installed in the ROKU devices is proprietary. It will NOT work with non-ROKU devices. That's why I attached a non-ROKU blue-tooth transmitter to the audio out port on the TV, and then attached the speakers to it. I have even attached my Echo systems to it. Bluetooth transmitters are relativity inexpensive.
P.S. You can still use your ROKU speakers, but hookup your non-ROKU speakers to a a blue-tooth transmitter attached to audio out port on your TV. Whether the sound will be in sync is a different issue. You can try setting the audio settings on the TV to PCM.
I sincerely hope Roku is taking feedback to update their firmware/software to open back up to third party Bluetooth speakers. Having to purchase an adapter, Roku specific speakers or go through a ridiculous workaround with mobile Bluetooth app functionality really takes away from the experience of using the TV. Unless things change, I am another customer who has no intention to put more money into Roku products given this. Instead, I’ll save up for a another brand and eventually trade in my new TV for one that doesn’t require annoying workarounds to pair with other products I already own.
Please be aware that pairing Bluetooth devices to your Roku TV is only supported if you are using the Roku TV Wireless Speakers, or the Roku Smart Soundbar in combination with your TV. You cannot pair Bluetooth devices to your TV on its own—this functionality is not supported.
We do offer a feature called mobile private listening through the Roku mobile app. If you were to pair your Bluetooth audio device to your mobile phone, then activate this feature in the mobile app, you could play your TV's audio on your Bluetooth device using this method.
For more information, see these additional resources: