Part of the reason you can recognize the distinct flavor of a single-origin coffee or an espresso blend is due to a chemical process known as the Maillard Reaction. At the dawn of the 20th century young Louis Maillard was intently recording his studies of chemical reactions in foods as part of his PhD thesis.
Consequently he is credited with revealing a complex series of continuous reactions between amino acids and reducing sugars at various low temperatures now called the Maillard Reaction. Like caramelization it is a form of flavor development and non-enzymatic browning in many foods including coffee. (Hmm... perhaps he should also have a moustache named after him. What a distinctive curl!)
During the Maillard Reaction flavor compounds are constantly created, then evolve, and reform into new flavor compounds. And in the case of coffee roasting, desirable flavor development is a combination of Maillard Reactions and caramelization.
Although studied now for almost a century, Maillard Reactions are so complex that much is still unknown. So many factors are important and contribute to the Maillard Reaction process to form color and aroma like the types of sugars and amino acids present in the coffee bean, the acidity or pH, and the presence of oxygen, water, and other elements, and temperature.
As the Maillard Reaction progresses many complex chemical products are created including flavor compounds and brown pigments called melanoidins which besides contributing color may have some beneficial anti-oxidant properties.
For coffee roasters the Maillard Reaction and caramelization are desirable effects as both convert sugars to a furfuryl and furans in coffee contribute a caramelly, slightly burnt and also slightly meaty flavor note.
So now you know that a Maillard Reaction contributes to the body, flavor and aroma of your daily cup of Joe and does nothing for your moustache!