Have a 99 RR that came to the US from Canada and has the displays in Km. Is there a way to switch the odometer display from Km to miles?

 

I believe that it can be programmed in via Rovacom or other compatible interfaces. Before you head off to the stearlership see if an independant shop has the appropriate hook up to talk to your computer.
While your at it btw, you could also ask them to reset the display language to English.