Position oven racks in uppermost and lowest positions; preheat to 450°F. Line 2 large rimmed baking sheets with parchment paper.
Whisk 3 tablespoons oil, 1 tablespoon mustard, 1 teaspoon each pepper, garlic powder and paprika and ¼ teaspoon salt together in a large bowl. Add sweet potato pieces, fennel slices, carrot slices, 2 cups squash and 2 cups Brussels sprouts; toss to evenly coat. Divide between the prepared baking sheets; spread in an even layer
Roast until tender and browned in spots, stirring and rotating the pans top to bottom halfway through, 20 to 25 minutes. Sprinkle with 1 tablespoon herbs and the remaining ¼ teaspoon salt.
