Nearly all waterproofing systems need protection against the effects of ultraviolet rays in sunlight and weather conditions.
Where the roof will not be subjected to regular pedestrian traffic protection it can be provided by bitumen based paints the reflective type, eg. silver roof paint, aluminium paint. Or by covering with crushed stone on protective lining, to protect the waterproofing. This will require frequent maintanence.
Where pedestrian traffic occurs, one can use tiles, concrete, pavings and stepping blocks to protect the waterproofing and ensure proper drainage.