How can I inspect and repair a roof with moss and other greenery on it?
It's probably time to replace the pantry roof. But first, you need to understand how so much water got there that plants started growing on it! Is the pantry roof a much lower slope than the house roof it's attached to? How's the flashing between the house roof and the pantry roof? Are you in a rainy climate? Could the slate roof be leaking water onto wood framing or decking beneath the slate? What are the plants consuming for nutrients? Most things don't grow with only water... are they rooting in some wood?