Various way to roast coffee but here is the easiest. You will need a popcorn maker and green coffee (BTW green coffee has a shelf span of at least a year). DO IT OUTSIDE as it makes quite a bit of smoke by the end. Start the pocorn maker for a minutes to warm it up then put about 100 grams (1/4 pound) of green coffee in the popcorn maker, bean will go from green to beige and then to light brown, the beans will start popping thereafter. Basically the bean shells are exploding to release moisture, if you like your beans lite roasted you can stop there otherwise continue the roasting process. A little while later you will hear a second pop, this is when the beans cell structure change and beans become oily. You should not roast your beans longer than the end of the second pop otherwise the sugar within the beans will burn off. That level of roast is called the Starbucks roast

. That it, just roast your beans to the color you like and enjoy 24 hours later. The whole process takes about 10 minutes.