Those who have tasted coffee using this roasting method would attest that hot air roasted coffee beans are superior in flavor to drum roasted beans.
Not unlike a hot air popcorn maker, a hot air coffee roaster circulates the beans around the roaster with hot air, which propels them through the roasting process. A natural gas burner provides heat for the roasting process and the hot air moves the coffee, rather than the roaster manually moving the beans (in the case of drum roasting).
In the conventional drum roasting method used by most roasters, a hot steel drum is what moves the coffee beans, which tends to scorch the beans. The beans are added to the roaster at extremely high temperatures and water begins to immediately evaporate from the them before the sugars are allowed to caramelize.
Plumes of smoke when drum roasted coffee is released from the roasting chamber into the cooling bed. (You won't see this with the hot air roasting method.)