The secret to the wonderful flavor of Vietnamese coffees is undoubtedly the coffee roasting method. Beans are roasted slowly at lower than standard temperatures so that the beans do not burn. Roasting slowly in that way causes the beans to have a dark color similar to dark roasted beans but with one big difference—while dark roasting can burn away the oils that give coffee its flavor, slow roasting seals in the flavor, creating a much stronger aroma in the bean, and a much fuller flavor.