Instructables user 'nightlife31' has modified a simple popcorn make to instead roast coffee using some imagination, Arduino and external hardware. By controlling the speed of the fan in the popcorn maker, the temperature of the beans inside can be controlled - and an excellent candidate for automation. The results are effective and you can also control and calibrate the system with a PC as they're using the PID library. Please note that this project involves working with mains current which is dangerous to say the least, and that all work must be completed by a licensed electrician.
When making your own version of the coffee roaster, consider the Freetronics LCD & Keypad shield which contains a bright 16x2 character LCD and five buttons that can be read from only one analog input pin: