Hi, I find out the next few things:
One, chromecast limits the output to 24bit/48khz.
Second I installed Roon remote apk on my Nvidia Shield android TV. Than there no limits. Best quallity to connect to my dac (fiio k5pro).
So my request is, Roon remote needs to be available on AndroidTV Shield! Now it is very difficult to navigate. Only with nvidia android remote.
An other thing is see, when I have a 96khz source it is downmixed to 48khz (Chromecast Shield). And than the Shield it upmix to 192Khz. That is why android tv remote app is needed.