Is tea ceremony always held in tea ceremony rooms?
The tea ceremony is usually held in small chashitsu which is located near a small pond, a green Japanese garden and path with tobira ishi (stone path). The most typical tea ceremony room is Tai-An built by Sen no Rikyu in 1582 in the Myoki An temple of Kyoto.
The tea ceremony is not always held in chashitsu. Almost all Budhist temples occasionally organize tea ceremony gatherings in their Japanese style rooms called hiroma.
Ryurei style rooms.
The tea ceremony rooms do not always have to be in Japanese style tatami rooms. If there is a misonodana (a desk-like set up that has the tea boiler) the tea ceremony can be held in a Western like room where the guests are sitting at a table.
Naodate style tea gatherings. Especially in the spring and summer large tea ceremony gatherings are held outdoors. This type of tea ceremony is called naodate.