A penetration pocket, useful to seal roof openings at protruding pipes or the like, is made of a material compatible with roofing asphalt. The penetration pocket material is asphalt-based with polymeric materials added to impart strength and toughness. Fibrous material may also be added for increased strength. The roofing asphalt, when applied around the penetration pocket, fuses with penetration pocket walls and base, and upon cooling, the penetration pocket and the roofing asphalt are welded together to effect a secure, water-proof joint.