Is there a difference between filter and espresso roast?

There is a real difference and it is smaller and less rigid than the labels suggest.

What an espresso roast usually is

Roasted slightly longer or further into development, for two reasons.

Solubility. Espresso has 25 to 30 seconds of contact, against several minutes for filter. A more developed bean dissolves faster, so more comes out in the short time available.

Acidity. Nine bars concentrates everything, including acidity, which can read as sharp. Slightly more development softens it.

Body. More development generally means more perceived body, which matters in milk.

What a filter roast usually is

Lighter, to preserve the delicate aromatics and acidity that a longer contact time can afford to extract gently.

Why the line has blurred

Modern specialty roasters increasingly roast omni — one profile intended for both — usually towards the lighter end. Combined with better grinders and finer control, light roasts as espresso have become normal rather than eccentric.

What it means practically

Filter coffee as espresso works, and needs a finer grind, a hotter brew and often a longer ratio. It is where turbo shots came from.

Espresso roast as filter works and often tastes flat, since there is less acidity left to reveal.

Buying

Ignore the label and read the roast description. “Light and floral” tells you more than “espresso”.