Hi Joachim! Well, talking about roasting beans is a huge subject: just consider that is something you can easily do at home (with basic results) or doing it in a professional enviroment, roasting with professional machines.
But let's start with the basics: if you want to roast for fun, just to try it, you can easily put the green beans on a pan, put it on the stove, and let the magic happens! It will be really similar to the old-school pop corn makings, you will soon hear the beans starting to pop, and when they're the color that you want, they're done.
Of course this is really home made, and you cannot control the quality at all. If you want to start roasting beans to become a professional, the best suggestion I can share with you is this: go to a roasting class, learn at least a little bit of the basics (a lot of chemistry involved), and then if you're sure about it you can buy a small coffee roaster, and start playing with it!
You can find nice, small but professional machines starting around 1K, and then if you find out that's really what you want to do, you can easilly upgrade it to something bigger.