Room banners can be system wide (ie: A free $10 voucher with every booking made this month) or specific to a Room (accommodation type).
If you want to create a Room specific banner you will first need to create a banner in Admin Menu | Room Banners. Banners are for a set time, and have a particular style as set in the room banner area. See ‘Room Banners’ for instructions. Once you have set up a banner you can go to the Room, Room Banners, New. See examples below for some styling options: