The researchers studied how Arabica and Robusta coffee beans are roasted using a rotating cylinder tube roaster with an electric heat source. They found that roasting at 205°C for 78 minutes resulted in a dark roast level. The color of the beans changed significantly, with moisture content decreasing from around 12% to about 3.5% after roasting. Arabica and Robusta beans showed different color changes during the roasting process.