If its has hdmi input and then has RCA output, it would allow you to see your Roku soundbar on an old tv. You can only play programs from channels built-in to the streaming device in the Soundbar. You won't be able to hear sound from other devices connected to your tv through the Roku Soundbar.
If the convertor is RCA input to Hdmi output then that is useless. See they're not backwards compatible.
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