Ask ten people what "dark roast" means and you will get ten answers, most of them about strength. So let's clear the biggest one first: roast level is not strength. Strength is how much coffee you dissolve into how much water — a ratio you control at the brewer. A light roast brewed at 1:14 is "stronger" than a dark roast at 1:18. What roast level actually changes is chemistry: how far the beans were taken through the cascade of browning reactions inside the drum.
Light roasts are pulled shortly after "first crack" — the audible pop when steam pressure fractures the bean. Stop here and the coffee keeps most of the acids and aromatic compounds it grew with: florals, citrus, berry-like fruit. This is why we roast our Ethiopian and Kenyan lots light. The origin character is the point, and every extra second in the drum trades a little of it away for roast character.
Keep going and sugars caramelise, acids break down, and body builds. Medium roasts — our blends live here — are the trade's handshake: enough development for chocolate and nut sweetness, enough origin left to taste where it came from. Push further toward dark and the flavour of the roast itself takes over: bittersweet, smoky, ashy at the extreme. At that point most coffees taste alike, which is precisely why commodity coffee is roasted dark — it hides sins.
None of this makes light "better." A washed Huila at medium is a more honest, more delicious cup than the same lot roasted light and sour because someone was chasing fashion. Roast level is a decision about what a specific coffee has to say — our job is to develop each lot far enough to be sweet, and no further.
So read our labels this way: light means the farm is doing the talking, medium means the roast and the farm are in conversation, and medium-dark means we built the cup for milk, espresso pressure, or both. Strong is up to you and your scale.