Some fun facts about decaf: since caffeine gives coffee the majority of its bitterness decaf tends to be much sweeter, the decaf process affects the cellular structure of the bean so that even at light-medium roasts you'll still get surface oils whereas with regular coffee you'll only get that with a dark roast, also with some decaf coffees you'll get a very savoury smell (like meat) after roasting
Left: decaf coffee before it's roasted. Right: regular caffeinated coffee before its roasted.
