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:
Edmund
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