I am poaching this question from my inbox because I encounter it frequently. Let us start broad: what is the difference between espresso and filter?
Espresso refers to a type of preparation. Espresso’s origins are in the 19th century with attempts to shorten brew times using pressure from a water boiler. Its name makes a lot of sense, right? What emerges along a long line of competing patents, innovations, and prototypes is a machine that drives a burst of water through a portafilter of ground coffee to create a small, strong coffee. Pressure, fine grinds, and brew ratios concentrate flavours, meaning balance is crucial. A tinge of underdevelopment becomes hot celery soup. A baked coffee dries the mouth like feta cheese. Any unbalanced acidity will hulk smash the palette and obliterate sweetness. Moreover, espresso is often the base for milk-drinks and anything too acidic will most certainly clash. Grapefruit juice latte anyone?
Filter on the other hand, uses gravity (and in some cases agitation) for extraction. This usually means courser grinds and larger brew ratios (but see a couple weeks ago for the 1:16.5 golden ratio). Generally, it is less intense and provides leeway for sour flavours to co-mingle with sweet notes. At its best, it can mean more complexity and a better window into origin.
For roasters, this usually means people blindly go darker on espresso roasts with the presumption that it will be more soluble and have lower acidity. This does not always work, as Matt Peger illustrates the inner bean of dark roasts can be underdeveloped. At Cut, I follow Scott Rao who states, “The goal when roasting for any brewing method should be to create the desired balance of sweetness and acidity while maximizing development”. For our espresso, I push development ever so slightly (using factors like charge, total roast time, and airflow) to ensure solubility and a profile that will take milk well. My filter profiles aim for the same balance but will highlight those crisp and clean acids in higher concentrations. In either case, sweetness and showcasing origin is the goal.
tl;dr: For brewing filter, use our filter or espresso roasts. For espresso extractions, use our espresso. Avoid our filter for espresso preparations because milk. Lastly, never trust a roaster who adds roast to espresso profiles just because it is espresso or one that allows green underdevelopment because it is filter.