You need a left join to try and find rooms without an applicable reservation record.
SELECT
ROOM_DESCRIPTION_DESC AS "DESCRIPTION",
COUNT(ROOM_DESCRIPTION_ID) AS "AMOUNT"
FROM ROOM_TAB
JOIN ROOM_DESCRIPTION_TAB ON ROOM_DESCRIPTION = ROOM_DESCRIPTION_ID
LEFT JOIN RESERVATION_TAB ON RESERVATION_ROOM = ROOM_ID
AND RESERVATION_FROM NOT BETWEEN '2014-02-10' AND '2014-02-11'
WHERE RESERVATION_ID IS NULL
GROUP BY ROOM_DESCRIPTION_DESC