Hi @megumi35,
Greetings!
Thanks for sharing your interest in the Roku audio devices, and we'd be more than glad to assist you with this. Since you wish you connect a Roku Sound bar to your Roku TV, it's best to check if it's a certified Roku TV and Sound bar ready. To determine if your sound bar is Roku TV Ready certified, look for the certification logo (seen below) on the original packaging or user manual, or visit the product details page on the manufacturer's website.
For more information regarding the set-up: kindly visit the official Roku support article at this link here.
If you have further questions or inquiries, feel free to reach out to us. We're always happy to help.
All the best,
Kash
Takashi O.
Roku Community Moderator