New to Sonos Playbar world, how to get ROKU to do 5.1 sound

I'd think that you might start by looking at Roku's help page:

https://support.roku.com/article/208754498-how-to-set-up-your-roku-streaming-player-or-roku-streaming-stick-for-surround-sound

Then I'd go in and check the audio settings on your Samsung TV to be sure that it's set to Dolby Digital on the pass through.

My samsung TV doesn't allow me to set on dolby digital, it is greyed out

Then I'd recommend you chat with the customer service folks at Samsung, and figure out why.

its a fairly common thing for tvs to currently not offer pass through 5.1, therefore I think I need a workaround, I don't think samsung will get me very far.

Hmm. That's news to me. I'd have thought most modern TVs would offer pass-through, though I'll admit I haven't shopped for a TV in a few years. There's quite a few threads around here about Samsung issues, but the search function on these boards are persnickety. Perhaps do a google search for others with your particular TV and Sonos, and see what comes up?

The alternate workaround, also mentioned in many threads on this board in many places, is a optical splitter/switch that is inserted before the TV, which takes HDMI input, pulls out the optical output, and then sends the video signal out to the TV via HDMI. Flexson makes one, but there are many here who use one made by a company that starts with an O (Optima? I just don't remember, since I don't own one). You could do a search on Amazon for HDMI Switch with optical out, and probably get a list of a few, and pick one that tickles your fancy.

What's the model number of that Samsung TV? We can check for you if it's able to pass DD5.1 over optical.

Its Samsung un48h6350af, thanks for checking

According to the review here that TV is unable to pass 5.1 from HDMI to Optical Out. From what I've seen, almost all newer Samsung TVs are able to do this though.

An HDMI switcher with an optical out would probably be your best bet. Have the HDMI sources go to that switcher and then have that wired to your PLAYBAR

Would this work? Sewell Direct SW-30537 Lightwave 3x1 Optical Toslink Switch With Remote

Connect my optical out from both my TV and ROKU to this and then connect that to the Playbar? or some other technique?

It looks like you (RYAN S) are suggesting something like this: Monoprice 5557 4X1 HDMI Switcher Toslink & Digital Coaxial Port 3D support

How does my audio from my tv go to sonos using this? Do I connect my HDMI out from my TV and HDMI out from ROKU to the HDMI in on this and connect only the optical out to sonos?