Room Types window is the main place where you may set prices for rooms. Each room does not have own pricing. Instead you need to split all rooms into groups - room types and setup the pricing based on room types.
Press Add button to create a new room type.
Select its name and price.
It's possible to use Price Schedule tab to create, for example, week-end or seasonal prices.
Specify how the room is charged in Charge Period field: Daily or In Check Out.