No, if your roku tv had rca jacks, or phonoplug to accept a breakout cable with rca jacks on it, in both cases the rca is an input, you need an output to send the sound to your soundbar. The only audio outputs on a roku tv are hdmi-arc or optical output. Sorry.
Edmund Roku Community Streaming Expert
Help others find this answer and click "Accept as Solution." If you appreciate my answer, maybe give me a Kudo.