Dark roasted coffee beans are quite suitable for making espresso coffee. Espresso beans are just ordinary coffee beans that have been dark roasted and designated for that type of drink. Espresso beans are dark roasted because darker beans are sweeter. The minute amounts of sugar inside the beans caramelize, making the espresso slightly sweeter and avoiding a bitter aftertaste.
Darker roasts are generally bolder because they have less fiber content and a more sugar flavor.