SQL Server 2019

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DECLARE @Hours TABLE(ID INT)
INSERT @Hours
VALUES
    (0),(1),(2),(3),(4),(5),(6),(7),(8),(9),
    (10),(11),(12),(13),(14),(15),(16),(17),(18),(19),
    (20),(21),(22),(23)

DECLARE @Schedule TABLE(RoomId INT, StartDate DATETIME, EndDateTime DATETIME)
INSERT @Schedule
VALUES
    (1, '2022-03-10 00:00', '2022-03-11 00:00'),  -- Different room
    (2, '2022-01-01 00:00', '2022-01-02 00:00'),  -- Before
    (2, '2022-03-09 22:00', '2022-03-10  8:00'),  -- overlap start of day 
    (2, '2022-03-10 10:00', '2022-03-10 12:00'),  -- mid-day
    (2, '2022-03-10 14:00', '2022-03-10 15:00'),  -- mid-day
    (2, '2022-03-10 16:00', '2022-03-11 08:00'),  -- Overlap end of day
    (2, '2022-04-01 00:00', '2023-04-02 00:00')   -- Full day After

DECLARE @RoomInput INT = 2
DECLARE @DateInput DATETIME = '2022-03-10'

SELECT H.*
FROM @Hours H
CROSS APPLY(SELECT DatedHour = DATEADD(hour, H.Id, @DateInput)) DH
WHERE NOT EXISTS (
    SELECT *
    FROM @Schedule S
    WHERE S.RoomId = @RoomInput
    AND S.StartDate <= DH.DatedHour
    AND S.EndDateTime > DH.DatedHour
)
ORDER BY H.Id

ID
8
9
12
13
15