Hi Mark,
Altering the bit rate and resolution capabilities of your software and hardware won’t change the sound until you feed your system source material with that bit rate and resolution. That can be hi res files or upsampled Redbook files. Download a few free hi res files and see if you like what you hear.
Roon doesn’t have options designed to change the sound. It has options for different ways of interfacing with hardware. Sometimes people hear audible differences from them, but it’s usually not a huge difference. Roon tries to be bit perfect (purple signal path light) leaving any DSP to the user.
This KB page sets out the various options in Roon and describes what they are for.
Streaming to a Chromecast Audio endpoint is intended to be supported, but no timeframe has been announced.