In general, there are multiple ways to connect a soundbar to a TV. It's not really a Roku issue. The short answer is to connect the soundbar to the TV's HDMI-(e)ARC port if the TV and soundbar support it and the Stick to one of the other TV HDMI inputs.
Without ARC, see this post for my explanation for someone with Samsung products. It may not apply to your soundbar and TV, but it gives you some idea of how these things can connect.
https://community.roku.com/t5/Roku-setup/Ruko-streaming-stick-setup-with-Samsung-tv-and-soundbar-usi...
If you want to provide the model numbers of your TV and soundbar, I'll look them up for you.
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