Preheat. Preheat the oven to 425°F and line a baking sheet with foil or lightly grease.
Mix seasonings. In a small bowl, combine the Italian seasoning, paprika, rosemary, sage, salt, and black pepper.
Prep vegetables. Place the potatoes and Brussels sprouts on the baking sheet. Drizzle with 2 tablespoons olive oil, add the minced garlic, and sprinkle with about half of the seasoning mixture. Toss to coat, then spread into an even layer, leaving space for the chicken.
Season chicken. Arrange the chicken thighs skin-side up on the pan. Brush with the remaining 1 tablespoon olive oil and sprinkle evenly with the remaining seasoning mixture.
Bake. Bake for 30 to 35 minutes, or until the chicken reaches an internal temperature of 165°F and the vegetables are tender and browned.
Rest and serve. Remove from the oven and let rest for 5 minutes before serving.
Notes
Even cooking. Cut potatoes to uniform size so they roast evenly.
Potato skins. Red and Yukon gold potatoes do not need peeling; russet or sweet potatoes should be peeled.
Make ahead. Assemble on the baking sheet, cover, and refrigerate for up to 4 to 5 hours before baking.
Storage. Store leftovers in an airtight container in the fridge for up to 5 days and reheat before serving.