This page explains how to create a virtual roomtype with multiple rooms from a number of individual rooms.
'''Example''': You have 3 real rooms all updated individually at a channel like Airbnb. You also want to sell them on Booking.com or other channel but they require a "roomtype" with a quantity of 3.(this example will work with any number between 2 and 12 individual rooms)
It is assumed you already have the individual rooms each with a quantity of one, if not, create these first.