In order to avoid charring the beans, agitate them intermittently – every minute or so – during roasting. Try not to leave the oven door open too long to avoid letting the heat escape. After about five or six minutes, you will hear the “first crack.” Technically, the coffee is now lightly roasted. Depending on how dark you like your roast, wait another minute or two, then start checking the beans for color. Use a roasted coffee you like as a guide. Once the beans begin to reach that color, you can remove them from the oven. If after 12 minutes, the beans aren’t browned yet, increase the heat to 525 degrees F.