Beans are not easily observed as other methods.
Oven vents smoke.
All ovens produce uneven roasts, which can actually add to the complexity of coffee flavor, but plain ol' electric ovens will roast too unevenly. Roasts more coffee per batch than any other method. All you need is a stainless steel wire mesh collander or a perforated pan and an oven. The later is by far the best, allowing greater air movement around beans and producing more even roasts. For vegetable steamer, place on cookie sheet and cover with coffee beans spread only one layer deep.