In Alpha; 1.0 there are exactly 3 rooms that you can place, plus a forth room that cannot be placed.
Cost: 10 Gold
Description: This room can not be used to produce any resource. It does have a very nice window though.
Cost: 20 Gold
Use: Production of secondary currency (wood).
Description: This room activates a wood production system when a gofer works inside it every 20 seconds. At some point it may detonate after being destroyed by enemies in a later model.
Cost: 20 Wood
Use:Transfering 1 wood to gold every second.
Description: This room activates automatically and begins tranfering wood into gold. There can only be one vault room in your fortress at once.
Use:Trains Gofers into soldiers
Description: By left clicking the room after it lands, you can send a gofer to train to become a soldier. By clicking twice or double click you can send two gofers to train. After they become soldiers, click the soldier to mobilize it.
Cost: Can't be purchased
Use: Creating gofers by left clicking.
Description: This is the only room that appears at game start without purchase. It can't be purchased at all. If your portal roomis destroyed than game over, destroy th opponets Portal Room to win. If you left click your portal than it delivers a gofer for the right price.