Based on what the image suggests on the Epson website, it is hard to tell what that audio output is. The specifications suggest it is a 3.5mm jack, which of course is stereo, and not 5.1. 

I’m unsure where you would connect an optical adapter to. In general, I would think some sort of 3.5mm to optical adapter would probably work. The adapter would plug in to the 3.5mm audio out port on the projector, and then convert the signal to optical, which would then be connected to the Sonos Ray.

But honestly, I think there is an easier, more efficient, and ultimately better way to connect the Sonos Ray, which has been covered many times in this forum. Simply put an HDMI switch with an optical audio out in line with the input HDMI stream, and pull a full 5.1 signal out of the optical port of that adapter to feed the Sonos Ray, so that the audio never comes from the projector. 

Thank you very much for your comment. I happen to be projecting via Miracast, so the HDMI switch is not viable. In the attached images are the ports of the projector and the adapter I am using. But it doesn't want to work for me. It's frustrating.

Could you be more clear about what the red and white RCA cables are connected to? The only audio out I see on that projector is the. 3.5mm ‘headphone jack’ output.