Generally, the beans are roasted at approximately 400 degree, the process increasing the bean's size by nearly 50% while greatly reducing their weight. Roasting caramelizes the sugars and carbohydrates within the bean, creating 'coffee oil', which gives coffee its flavor and aroma.

Lighter roasts tend to produce sharper, more acidic coffee with more caffeine. Darker roasts have a fuller, bittersweet tang, with caffeine and acidity decreasing as the roast darkens. Common roaster lingo for classifying roasts (from light to dark) are: Cinnamon, Medium High, City, Full City, French and Espresso/Italian roast.