It’s a dark roast, a simple roaster’s definition of is that it is entering second crack, the second time during the roasting that the beans make a crackling sound, first with the release of steam and now with the release of carbon dioxide.
The beans are going to be dark on the outside but you don’t want the interior of the bean to be as dark because that will mean your coffee will taste more like ash. You want it to be lighter because that will reflect taste. Let’s recognize that a dark roast has roasted a significant proportion of the flavor of the beans up and out of the chimney.
A coffee bean that is denser and thereby harder in its organic structure than another, for example an almond nut is denser than a cashew nut, will inevitably take more heat. A hard bean is therefore a tool in the recipe of a dark roast. You can still get flavor from the interior as compared to the exterior of the bean that has received the full punishment of direct heat. You thereby get roasty flavours from the outside of the bean and toasty from the inside. You are getting dark roast complexity by this strategy of adopting the harder bean.
If you use say three beans on the blend of slightly different densities then this will increase flavour complexity, though the range of flavours at the dark end of roasting are narrow.