I recently purchased a Roku TV and got rid of Dish Network. I used to be able to send the audio from the Dish receiver to an AM/FM tuner/amp and out to some outdoor speakers. The tuner/amp has only RCA inputs-- no HDMI or Optical. I connected the Roku TV RCA jacks to the tuner/amp RCA Aux jacks, but got nothing. I tried an HDMI to RCA converter, and that didn't work either. (I have a sound bar connected via the TV's HDMI-ARC port and works well.) I next tried an Optical to RCA converter. I did get sound to the outdoor speakers, but it was only a buzzing, pulsing static. I then changed the TV Audio setting from Auto to TV speakers and that worked well. The soundbar is disabled, but audio now plays through the TV speakers and the Tuner/Amp to the outdoor speaker system. (There is a noticeable slight delay in the audio to the outdoor speakers). Only problem is when not using the Tuner/Amp>Outdoor speakers, I have to change the TV Audio setting back to Auto to use soundbar. Anyone have better ideas?
I notice you say “RCA jacks” but you tend not to use words like “input and “output” so I wanted to mention that in the audio/video world, nearly all jacks are directional. For example, I googled up a picture of some random Roku TV (probably not your model) and I see some RCA jacks, but they are labeled “A/V In”. So on that particular Roku TV, those are for getting signal FROM something IN to the TV. So, that might explain some of your “got nothing” experiences.
Thanks for your reply-- On the Roku TV that I have, the RCA connections are labeled 'Video, L, and R'-- no indication whether they were 'In or Out'. I thought it was worth a try, but it didn't work.