a reusable grid system and method for in place cast forming a monolithic roof covering for a sloped roof , the roof covering having the stepped and segmented appearance of a tiled roof . the grid system includes a plurality of horizontally disposed dam bars and transversly disposed spacer bars which , when removably assembled atop a sloped roof , are adapted to retain monolithic poured and scraped plastic uncured concrete or the like so as to have an exposed surface which substantially duplicates a conventional tile roof after curing and removal of the grid system . the cured roof covering is monolithic from one eave to peak to the other eave and may include foam - filled cavities for thermal insulation and weight reduction , longitudinal segmented elastomer - filled expansion joints , formed eaves with gutter connecting means and molded edges .