Abstract: A clamp for a roof device such as a sleeve for a pipe protruding from a roof having a sealing sheet. There is a skirt, the underside of which abuts a surface of the roof and which underlies the sealing sheet. There is a clamping ring and the sheet is sandwiched between the ring and the skirt. The ring has two lower edges having a downwardly directed concavity defined between them such that a first of the edges abuts the sheet so that an upper surface of the ring may be pressed downwardly by a fastener to press the edge against the sheet to localize compressive forces between the edge, sheet and skirt to seal against entry of water between the sheet and skirt. The device disclosed is a pipe sleeve of spun aluminum. There is a circular base ring adhesively fastened to the underside of the skirt and the clamping ring is circular and of flexible aluminum, with a crescent-shaped cross-section. The arrangement is such that the circumferential edges of the clamping ring are coextensive with the circular base ring.