Or really why?
I can give you a couple of good reasons. First off, if you're interested, read this post. Basically it wasn't easy for me to find green coffee beans at a good price in South Florida. Part of the reason I'm writing this is that someone may say, Hey you dumb Moose, just down the road a piece you can find all the beans you want!
I ended up going all the way up to Boca, had a great Indian meal in the Whole Foods, and got a pound of green beans. Or rather Green Unroasted Coffee Beans.
Now that you have the things, how do you roast them? Our forefathers roasted their coffee beans on a cast iron skillet that was warmed over a fire. I'm nowhere near that creative or that brave. Being a computer guy, and the one you usually call when your machine crashes, I like things much more controlled than combustion warming a slab of iron.
What you need to do is get into your car and go to a thrift shop. Why a thrift shop? Because the hot air popcorn popper is the ticket. They just aren't all that common these days. I got mine at a thrift shop here and it worked just perfect. The Holy Grail of Coffee Roaster Hot Air Popcorn Poppers is the "Poppery II". I got mine for six dollars.
Why is a poppery II so great for the task? The poppers are made with a small basket into which you pour your kernels, or coffee beans. The best ones have a solid bottom to the basket, and vents into which hot air is blown. The vents should allow the beans to spin around like something in a toilet that has just been flushed. You want a circular whirlpool motion. The Poppery II has the vents all facing the same direction and you get a nice agitation out of that.
Second you're going to want a coffee grinder. I have good luck with the cheap ones that you plug in the wall, fill with roasted beans, and press the lid down on a contact. They make a horrible racket, scare the dog, and will turn beans to espresso grind in about fifteen seconds.
You will want a large bowl to pour the hot coffee beans once roasted into a bowl as well, but I'm sure you have that.
Basically it cost me $11 for the beans, $6 for the popper, and $15 for the grinder.
How does it all work? Keep checking back. I'll post that later!