Thanks for the help! I was mostly looking for a confirmation or clarification that roon via chromecast requires loading a script from roonlabs.com.
@brian replied in the thread linked above that this is how it works. So far, I have zero luck with any device running google cast 2.0, and I assume the reason is that google cast 2.0 is moving away from the webpage based receiver app so it wouldn’t load the script anymore. So I thought the question is better addressed to Roon. At the very least, I would know which company I should submit a feature request to.