A single layer of asphalt roofing shingles on a small house - 1500 square foot roof (150 squares) would require a 10 yard dumpster. Roofs up to 3000 square foot (300 squares) would need a 20 yard dumpster.
If multiple layers need to be removed, multiply the size needed by the number of layers.
For example, a 3000 square foot roof with 2 layers to be removed would need:
20 yards x 2 = 40 yard dumpster.