There is no sound coming out of the Rosetta 200

First, try doing a hardware reset of the Rosetta: How do I reset Rosetta 200?

Check the front panel button settings. For example:

Make sure the Source to Analog Outputs is set to the appropriate selection. For example, if you are using the X-Symphony, X-FireWire, or X-HD option cards you should set it to Option.

Are the cables and connectors loose? Unplug cables from the ports in the back, then reconnect to make sure they are securely in place.