The specific temperature and time curve applied during roasting that determines a coffee's color, flavor development, acidity, body, and aroma. A skilled roaster develops unique profiles for each origin. Light roasts preserve terroir; dark roasts emphasize roast character.
The same Huila green coffee roasted light tastes of berry and flowers. Roasted dark it tastes of chocolate and burnt sugar. The roast profile determines what you taste more than almost anything else after origin.