The creator of a blog that describes itself as “a blog/dump of various projects, from simple daily tricks through microcontroller code to propane heaters that don’t really work,” has successfully repurposed a washing machine and propane stove as a drum coffee roaster.
According to the author, who goes by rxdtxd on the blog wemakethings.net, it takes some 60 to 90 minutes to roast beans. Here’s a basic description from the author:
The setup consists of the roaster itself, a propane gas stove, an electricity extension cord for the motor, and a big pan to rapidly cool the beans when they’re done (to prevent overroasting).
And here’s the coffee roaster in action: