When you set up your rooms, you can define a display order that will be included in your schedule on the back office side but also in the public calendar.
First, you need to click on the room menu and go to the file of your rooms
Click on the pencil on the top right to setup your room
At the bottom of the different setup fields, you have "Display weight", this is where you will enter 1 for the room that will be displayed first, 2 for the second and so on....
Don't forget to save your changes