'roofing' is formed by adding the suffix '-ing' to the English noun/verb 'roof'. 'roof' originates from Old English 'hrof', where 'hrof' meant 'roof; top'.

'roof' changed from Old English 'hrof' through Middle English forms such as 'roof' and eventually became modern English 'roof'; the verbal and nominal uses developed in Middle English and the gerund/nominal '-ing' form produced 'roofing'.

Initially it meant 'the top or covering of a building'; over time it retained that sense and also came to refer to materials and the process of covering a building's top, yielding the modern senses of 'roofing' as material and process.