I'm surprised, Oscar, that you would use the term Espresso when describing a type of roast. The degree of roasts for espresso change according to taste. I've roasted to just past second crack when the oil beads a little on the surface on some blends and the crema and taste was extraordinary. I do admit there is a range ideal for espresso, there is no one point in the range that is best.
Also, to say that a Dark roast is only good for espresso is not correct. A dark roast can add body to an otherwise thin cup of coffee.
We need to stress diversity in taste for coffee and it's roasts here in the USA. Us yanks have relinquished ourselves to a weak stale cup for far too long. So long in fact, that most yanks taste a real fresh,properly made cup of coffee and wonder what's wrong with it. When we, as professionals, pidgeon hole roasts and beans, the public follows suit and thinks that's how it should always be, thus cutting themselves off from another world of taste.