I called the one guy at Roland that totally knows their arranger products. He explained to me that the USB port is only to be used as a midi interface with a computer. It has no driver internally to do anything else. I also asked about using the USB device jack and he didn't think this would support this either. The midi jack could be used with a wireless midi transmitter and receiver but I don't think that's what you want to do.
_________________________
George Kaye
Kaye's Music Scene (Closed after 51 years)
West Hills, California
(Retired 2021)