A roof unit having an outer skin, an inward facing ceiling having a ceiling frame, and a basic structure. The ceiling and the outer skin along with the basic structure have joining configurations that mate together at corresponding locations. The ceiling has at least one fitting from a group of fittings including fittings for a ceiling cover, interior cladding, cushioning against impact, sun shields, an interior rear view mirror, interior lighting, wiring, operating and display elements, sliding, raising, folding, lamellar and glass roofs, and their frame parts and drive elements, and roof hand grips.