You do, that's who! Well, they certainly aren't for everybody; especially if you just want the caffeine jolt coffee provides without much concern for the taste or flavor.
Advocates of bean roasters claim that coffee tastes better when brewed shortly after roasting, and there is some validity to the statement. Once roasted, coffee beans begin to lose their flavors and quality and eventually become "stale."
By roasting your own beans at home, you can eliminate the chance that your beans are stale. In addition, you'll also need to grind your own beans after roasting, which leads to even greater quality as coffee looses even more flavor after grinding.
What does it cost to roast my own beans?The most obvious answer is it takes time to do this, about 20 mintues or so depending on your method and proficiency with the process.
Green (unroasted) beans generally cost less than their roasted counterparts, but different beans have different costs.
Finally, if you don't prefer to agitate your beans over an open flame, you'll want to invest in a quality appliance: a coffee bean roaster. Good household, non-commercial models, typically range from $100-$200.
Overall, you'll need to spend extra time preparing your coffee. However, your potential longterm savings from buying green beans along with a better tasting coffee brew makes roasting your own coffee beans even more worthwhile.
Amazon.com - Bean Roasters - Coffee bean roasters from the Internet's largest store. They also can offer extremely low prices because they sell a large volume of roasters.