Hi Vasileia, actually there are more ways to roast coffee at home, and it all basically depends if you want to do it properly or just for fun.
If it's just for fun, it's quite easy.
Grab a pan, put some green coffee beans in, put it on the stove and wait until it started to become dark and you hear a popping sound exactly like popcorns. It's the old school classic way, as they used to do before the advent of the proper roasting machines, and it's a method still used usually in poorer countries. It's not really reliable (you cannot control properly the temperature or the roasting degree), but it's really fun and the idea of drinking you own roasted coffee is really fascinating.
If you want to do something more professional, there are many different home roasters to try, starting from as little as 75€! Obviously the more pricy is the roasting machine (up to 1000€, and more), the more professional it will be, but at the same time the more knowledge will require from you.