Shredded Brussels sprouts look very pretty in a bucket, but if you're dead-set on whole or halved sprouts, that's OK too.
To make the shredded Brussels sprouts: Preheat your oven to 425°F and line two rimmed baking sheets with parchment paper. Trim the ends off of 5 pounds of Brussels sprouts, then use the shredder attachment of your food processor to shred them into thick slices. If you don't have a food processor, you can use a knife. Put the shredded sprouts in a large mixing bowl and toss them with 2 tablespoons olive oil, 1 teaspoon kosher salt, and freshly ground pepper, to taste. Roast for 30 minutes, turning the pans halfway through, until the sprouts are tender and browned on top.
If shredded Brussels sprouts aren't your thing, here's a classic roasted Brussels sprouts recipe.