You don't need an amplifier or audio receiver. The Rockville has a built in amplifier.
This TV doesn't have an analog audio output. You would need to convert the digital audio output to analog with a device like this Prozor
https://smile.amazon.com/PROZOR-Digital-Converter-Optical-Toslink/dp/B00KNNSKV0
You would plug the output of the Prozor into the Yamaha or directly into the Rockville.
To the Yamaha and then to the Rockville you would need two of these
https://smile.amazon.com/Hosa-CPR-202-Stereo-Interconnect-Meters/dp/B000068O17
To the Rockville directly you would need one of these
https://smile.amazon.com/JSAUX-Shielded-Gold-Plated-Smartphones-Speakers/dp/B07D8M5DML
Plugging directly into the Rockville means you would have to use the TV remote to change the volume of the music. Not a huge deal but it's another thing to handle.
Yup, that sounds right. Let me see if I can dig up the audio cable I'm using (I'd send the S-Video cable, too, but I don't know if it actually works yet).