The PC-USB input on your Rotel product supports two different audio classes.  USB Audio Class 1.0 is the original format and supports up to 96kHz audio. This is the default setting as all computers will support this class. USB Audio Class 2.0 is a newer standard and supports audio up to 192kHz. Not all USB hardware supports this format but most computers made in the last 5 years should support this.

Do note that if you are using a Windows PC for audio and wish to play 192kHz Audio, you will also need to install drivers on the computer to handle this. The USB audio drivers are included on a CD with the product, or they can also be downloaded here.