Preheat the oven to 400 degrees F (204 degrees C). Line an extra large baking sheet, or two jelly roll pans, with foil or parchment paper. (You can omit the lining if using a good non-stick pan like the ones linked here.)
In a large bowl, toss the brussels sprouts with olive oil, garlic powder, salt, and pepper.
Arrange the brussels sprouts in a single layer on the pan(s), making sure each sprout is touching the pan.
Roast brussels sprouts for about 25-35 minutes, tossing halfway through, until browned and slightly charred.
Optional step: If you want them even more browned or crispy, place under the broiler for 2-3 minutes.