There is nothing better than the smell of fresh roasted coffee except, perhaps, the smell of freshly brewed fresh roasted coffee. Some may call me a coffee snob but after roasting my own coffee beans at home for the last three years I have a hard time quaffing any other sludge that comes from beans that were roasted more than a few days before. Ground coffee from a can? I’d rather have instant. Even the whole bean coffee from the grocery store tastes like cardboard to me. You see, coffee is very much like wine. There is a great range of flavors and profiles depending on where it was grown, how it was harvested, the soil, the climate and finally how it was roasted. If you truly want to explore the subtle nuances of coffees you need to roast it yourself. Coffee flavors peak about 48 hours after roasting and then go on a decline – a much shorter lifespan than wine.
So, how does one roast their own coffee? There are several home coffee roasters on the market either using a hot air method (like a hot air popcorn popper) or a heated drum. The air roasters are the least expensive and can roast enough beans for a couple of pots of coffee. The least expensive is the FreshRoast Plus. It is simple enough but does not give you good control over the roast levels and it is easy to burn the coffee. You can find several places selling it for about $90 by doing a little bit of searching on Google. A step up from the FreshRoast is the i-Roast. It is also an air roaster but with a better design and it can roast up to a cup of green coffee beans. That is the one I have used for most of the last few years. It will set you back about $180 but it is worth it.
Raw coffee beans, so called “green beans” are generally cheaper than roasted beans and are much better quality. I usually order my beans from a place called Sweet Maria’s who go around the world sourcing small crop coffee. They have wonderful tasting notes and information on optimal roasting levels. You can find many other sources for green beans by doing a little searching. 
Here are some beans in the roaster. It has started its preheat cycle.
The temperature is rising and you can see the green color of the beans turning over into a tan and eventually brown color.
The HotTop will automatically spill the beans out into the cooling tray when the desired temperature is reached. These beans were roasted to a “Full City” roast which is just before they become very dark and shiny from extruded oils.
I can imagine how wonderful that must smell!
Do you need to roast them this way? Could you roast them stove top, stirring often? Or even in the oven (still stirring)?
My friend brought me some green beans from Guatemala, and I'd love to roast them at home, but don't want to invest in a "proper" roaster.
Some people try to roast them in a traditional air popcorn popper. There are a few problems with trying to roast coffee without a proper roaster. First is getting the roast right. Coffee beans need to be roasted up to about 420-428 degrees for that rich dark roast. It is hard to do that uniformly without some kind of specialized equipment. Also when roasted the coffee beans give off a lot of chaf and that needs to be removed during roasting. Whether it is an air popper or my drum roaster, these specialized machines have mechanisms for separating the chaf from the roasted beans. I would suggest that you first try the iRoast air roaster if you want to start roasting on your own.