A machine for roasting coffee. Or the person operating it! The basic requirements for a coffee roaster are a heating element that gets suitably hot and a mechanism for agitating the beans.: A mechanism for roasting coffee. The basic requirements for a coffee roaster are a heating element that gets suitably hot and a mechanism for agitating the beans. Broadly there are two types of roasting (i.e. heat transfer), The transfer of heat between matter. In coffee, conduction heating is contrasted with convection heating, which occurs in a moving fluid. More and Transfer of heat through the bulk movement of a fluid. In the case of coffee roasting, we discuss convection in the context of heated air moving as a fluid through a roast chamber. More. A A roaster with a rotating drum that provides agitation to the beans, while a heating element (typically either electric or gas) provides heat. The metal drum conducts heat to the beans, so drum roasters heat More will be mostly a conduction roast, but some convection as well. A hot air corn popper is a convection roast.