We believe that coffee should be all about the 'terrior', similar to wine.
The concept of terroir developed through centuries of French wine making based on observation of what made wines from different regions, vineyards, or even different sections of the same vineyard so different from each other. The French began to crystallise the concept of terroir as a way of describing the unique aspects of a place that influences and shapes the wine made from it.
Long before the French, the wine making regions of the ancient world already developed a concept of different regions having the potential to create very different and distinct wines, even from the same grapes. The Ancient Greeks would stamp amphorae with the seal of the region they came from and soon different regions established reputations based on the quality of their wines.
If you only roast coffee just enough to caramelise the sucrose in the bean, which off sets the natural acidity in the bean, it is possible to preserve the natural characteristics of the bean that reflect the terroir of the coffee and produce a excellent, albeit unique, espresso
As far as we can tell the practice of roasting the beans very dark is associated with using inferior beans whose unique characteristics are not particularly desirable and therefore you seek to minimise their presence in the cup by roasting the daylights out of the bean. The only exception is decaffeinated coffee where the green beans have already been turned a very dark brown colour by the decaffeination process, and end up being very dark after roasting.
While it is true that many coffees are not particularly suitable for use as single origin espresso, many others are. With single origin espresso there is nowhere for the roaster to hide. The margin for error is much smaller, as it can not be masked by subsequent blending. The demand on the roaster for accuracy and precision is much greater. As is the need for good, clean, green coffee, with low defect rates and well graded to ensure all the beans are of a similar size. Otherwise the small beans end up burnt and the large beans end up under cooked and a poor cup of coffee results (a classic case of two wrongs not making a right)