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Indonesia has an opportunity in developing the coffee processing industry, because apart from having a large market, it is also supported by potential raw materials. Therefore, strategic efforts are needed, such as downstream in order to increase added value and increase production capacity (Kemenperin, 2019). To determine the quality of the coffee can be seen based on two tests namely physical quality testing, and taste. Moisture value of coffee beans the maximum is 12.5%. One form of control is an increase in coffee processing technology, namely roasting machines (Maulid et al, 2021). This research focuses on forced convection hot air flow by a blower whose speed is engineered using the help of a dimmer speed controller to obtain optimal heat and mass transfer results by experimentally varying airflow and heat transfer then obtaining optimal speed and temperature values. Temperature also affects the value of the forced convection coefficient. The largest convection coefficient is found in the variation of the highest temperature value test, namely 297.5 ᵒC with a value of 43.66 W/m2 ᵒC. The lowest convection coefficient value lies in the experimental variation with an air flow velocity value of 11.4 m/s at a temperature of 297.5 ᵒC with a convection coefficient value of 28.38 43.66 W/m2 ᵒC. The convection heat transfer value (Q) will increase when the flame temperature (T) and air flow velocity increase (v). The greatest electric power will increase when the air flow velocity increases with a low flame temperature value. Effect of airflow velocity (v) and flame temperature (T) simultaneously on the final roasting temperature of 87.5%. [ABSTRACT FROM AUTHOR]