ARC means Audio Return Channel. It allows an HDMI out from a receiver to the TV, to also be an audio in back to the receiver. I don't use it myself – my setup is simple with each input device (Roku, etc.) having a simple HDMI to receiver connection and then the receiver has a simple HDMI to TV connection.
My devices all use just an HDMI connector – some may have an optical port but, if so, I have never used them. I'm not sure what you are using the optical connections for. My hazy memory is that people used an optical cable from the TV to the receiver before ARC if they wanted to have sound from the TV (such as over the air TV or smart TV apps) produce sound through the receiver. I only use my TV as a display so I don't need ARC or optical.
By the way, my TV and receiver are from 2008 so it's not a simple age issue.
I don't know what's going on in your system but I just thought I'd throw some data out there. The fact that you have both optical and HDMIs running may mean the receiver is configured in some way that needs to be changed. (Although honestly, I'd kind of expect your problem to be that the Roku has video and no audio in that case.)
So, are you not even getting the Roku UI showing? Or do you mean just video from shows is missing?
I found a picture of the back of that receiver, and I notice that there is an HDMI port labeled DVD. However, there is also a composite video port labeled DVD-in. So I wonder, if perhaps you need to configure it for which port is in use or if it selects automatically. And if it's automatic and something is connected to that DVD-in port, maybe it is selecting that video? All just guesses though!
