What is the Black pipe coming from roof into attic

this may be an old soil pipe or an old flu pipe

Hi, without seeing an image its difficult to tell 100% but sounds like to could be an old vent pipe from toilet waste piping. This regulates air pressure in plumbing pipes and allows sewer gases to escape to the outside mostly via your roof or roof vents. They can also be seen externally going past the guttering. Hope that helps

Impossible to tell without a picture. But as stated, it will 99% be either a old flue or soil stack

It could potentially be and old soil pipe, or fuel if large enough..