A coffee bean roasting machine of the type having a cyclone separator heating chamber and a coffee bean roasting chamber in a recirculating process stream driven by a recirculation fan is operated to air cool the roasted coffee beans in the roasting chamber, to a temperature beneath which the beans give off smoke, while at the same time incinerating smoke removed from the roasting chamber. A purge gate in ducting between the cyclone separator and the roasting chamber is opened to allow the flow of ambient air into and through the roasting chamber while blocking flow out of the cyclone separator, so that ambient air is directed through the roasting chamber. The smoke and any airborne particulate material from the roasting chamber are carried into the heating chamber and through the incineration tube, where they are incinerated. Preferably the system and process are operated automatically by a computer and programming.