Wow, this thread has gone from coffee grinders, to making espresso, to driving on highways in California, to cooking & eating BBQ, to roasting coffee & brewing beer.
I do not roast coffee beans in an oven. That would bake the beans, without roasting them. No electric kitchen oven I know gets hot enough for that. 'Baked' coffee beans suffer from being dried out, but still under roasted. It has been said that under roasted coffee tastes like baked vegetation or rotting grass clippings.
FWIW, I now roast with this
I don't know if propane gas grills get hot enough to roast coffee. I once met a guy who roasted coffee in a revolving mesh drum he rigged up with a built-in rotisserie motor in his grill. He liked the results, but I never tasted it. I wonder about using propane gas as a heat source, it produces a fair amount of water vapor as it burns, and does it get hot enough.
Most home methods use electricity for heat. There seem to be no limits to the DIY designs.
From what I understand, roasting coffee is best done with high heat, rapid heating, and rapid cooling afterwards. There are probably a lot of ways to do that. They range from the crude but effective
DIY heat gun – dog food bowl method, to
home roasters that cost $3,500.
When choosing a roaster, some criteria to consider are how much coffee you drink, your preferred roast level, and how much you want to spend.
www.sweetmarias.com
Also see this