Keeping the advantages and conveniences of an adjoining structure, attached gable / hip greenhouses slope in two or more directions, allowing larger, more flexible footprints for a given pitch and eave height.
Gable roofs have two opposing, sloped sides that terminate in a vertical wall that continues vertically to the ridge.
Hip roofs maintain a consistent eave height, with all three (or more) walls sloping towards a central point or ridge.