Go to SETTINGS->PROPERTIES->ROOMS->SETUP and set the virtual room to have the same characteristics of your individual rooms. Set:
*''Unit Allocation'': One per Booking*'''Sell Priority''' = Hide (to not show the virtual room type on your own booking page*''Overbooking Protection'': =Property*Use Prices From =Room 1 (to use the prices from room 1, alternatively you can use "This Room" and create individual rates for the virtual roomtype)
Go to SETTINGS->PROPERTIES->ROOMS->DEPENDENCIES and use the following settings for the virtual room:
*''Requires Availability in'': = Room 1 or Room 2 or Room 3 *''Combination Logic'': = Sum of all bookings *''Dependency Level'': = Ignore Sub Dependencies *''Assign Bookings to'': = First Available Dependancy Room *''Use Prices From'': Room 1 (to use the prices from room 1, alternatively you can use "This Room" and create individual rates for the virtual roomtype)