The roasting process of the coffee bean plays an important role in determining the flavours that you taste in your freshly brewed cup. Having an understanding of what roast to use with each brewing method can help ensure you enjoy every cup.
The coffee bean as a raw product begins as a green bean after being processed and dried. Professional roasters then use specially designed coffee roasting machines which heat and essentially cook the beans in the process bringing out the coffee oils. During the roasting process they are monitored closely throughout the process for their progress, a dark roasted bean will be 'cooked' for a longer period of time. Once the beans have achieved the desired colour they will be released into a cooling tray where they are agitated and cooled to stop the roasting process.
A medium roasted coffee will deliver a more mild and less robust flavoured coffee once brewed. This is partly due to the fact that the oils haven't been drawn out in the roasting process as much as they would be in a dark roast. Medium roasts are generally more suited to longer extraction methods of brewing such as a french press. This allows the good qualities of the bean to be brought out, while the acidity and bad qualities of the bean are less pronounced.
Dark roasted coffees will deliver a much stronger and more full bodied extraction, as the oils in the bean have been drawn out more during the roasting process. Shorter extraction times are suited to dark roast coffees such as espresso, as under pressure it will extract the great flavours and oils of the coffee bean while minimising the extraction of the negative bad flavours and acidity. The full body flavours of a dark roast will also complement drinks made on espresso.