Abstract: A roof jack apparatus for sealing openings in roofs through which penetrating conduits may pass. The apparatus includes an inner jack and outer jack. The inner jack may include an inner collar, a first flange, and an inner door. The outer jack may include an outer collar, a second flange, and an outer door. A portion of the inner jack may be inserted into at least a portion of the outer jack. The inner and/or outer jack may be rotated about each other. When rotated so that the first door is aligned with the second door, a passageway may be opened that allows the roof jack apparatus to be slid across the sides of the conduit and into position. The passageway may then be closed by rotating the inner and/or outer jack so that the first and second door are no longer aligned, thereby closing the passageway.