Hello @Egon,
Roon only sends >48kHz audio to devices that declare the HI_RES_AUDIO_SUPPORTED flag via the Chromecast SDK. If your device doesn’t report this flag, it’s basically stating that it doesn’t handle anything over 48kHz. If your devices support >48kHz sample rates and don’t report this flag, there is a bug in their implementation of Chromecast.
We are going to reach out to Cambridge Audio with this information and we will be sure to keep you in the loop.
-John