There's a big debate going on at the moment in term of roasting degree for espresso, the new trend seem to be going light on everything to preserve the Varietal flavour of the bean. But for me I think in the search for those "extra flavours" we have some how forgotten how an espresso should be like, I treat espresso as a "Hit", in other word it's how it makes feel rather than what I can taste in it. Texture for me is a lot more important in an espresso than Varietal Flavour, things like Syrupy, Velvety, Smooth and of course a nice strong Body to finish it off. Origin flavour is important for me... but not at the cost of Texture. A lot of the younger generation roaster seem to be scared of the second Crack in coffee roasting, fearing the change in wood structure in coffee may damage the flavour, but I actually think second crack increases the complexity for lots of coffees provided you don't go past rolling 2Nd crack (Vienna Stage), a lot of that chocolate flavour happens at this stage which I like very much. Which origin I don't like for Espressos? Mostly central American, they are flavourful and acidic, but most of them just doesn't seem to have that Texture I am after and the flavour is lost in milk anyway, they make a nice Plunger/Syphon coffee but not really for espressos or at least single origin espressos.
To compare espresso to Plunger/syphon is like comparing a shot of Tequila to a nice Chardonnay, Tequila will give you that "wow" factor like a punch in the face, while the Chardonnay is delicate and flavourful. Different drinks so we should also roast them differently. I like drinking Plunger coffee but I am an espresso man as I don't like to think too hard for flavours, if a drink is delicious it's delicious, end of the question!