Oxidizing roasting, the most commonly practiced roasting process, involves heating the ore in excess of air or oxygen, to burn out or replace the impurity element, generally sulfur, partly or completely by oxygen. For sulfide roasting, the general reaction can be given by:
:2MS (s) +  3O (g) ->  2MO (s)  +  2SO (g)
Roasting the sulfide ore, until almost complete removal of the sulfur from the ore, results in a dead roast.