I don’t know if ROC can do multicast on its own. I use the Pipewire source and sink. And I only do the one-to-one setup.
I did some tests in Pipewire:
Configuring multiple sinks is possible on a machine. They simply present as additional output devices. So if you want to switch audio to another source, that should be doable by switching to another output device.
Doing one-to-many: I don’t know if that is possible with ROC alone. You might be able to do something with Pipewire graphs