Can I make a request with Rotating Residential Proxies using a random country ?
Yes, you can. In order to send a request through a random country you need to navigate to the configuration of your membership and make sure that GEO is not added to the Settings - Special Services.
Another way to get random countries is to have the GEO service activated in the Settings - Special Services section, and no country selected in the GEO tab (both under Default GEO and also under Advanced GEO).