I've recently purchased an (Element) Roku tv, model M22109-MT. After plugging my Bose Solo 5 soundbar with the provided optical cord, I'm unable to adjust volume level with the roku remote, even after changing audio settings to 'optical'. Is there any way to accomplish this? Or am I forced to purchase a new soundbar that connects via HDMI?
Roku's remote only controls tv's, it's up to the Tv to control the Audio device via hdmi-cec. With optical only, you don't have to upgrade the Soundbar, just replace your Roku TV's remote with universal that controls the tv's and soundbar's. Like the One-For-All urc-7935, always much cheaper for open box ones on ebay:
urc-7935 remote: Search Result | eBay
Here is next to Roku tv remote: