Preheat your oven to 425°F and line a large rimmed baking sheet with parchment paper or foil.
Add the brussel sprouts and potatoes to a large bowl.
In a small bowl, stir together the olive oil, melted butter, garlic, thyme, and rosemary. Drizzle the mixture over the vegetables. Sprinkle over the salt and pepper and toss to evenly coat the vegetables.
Spread the brussel sprouts and potatoes on the prepared baking sheet, cut side down.
Roast the vegetables for 20 minutes, then flip and roast for another 10 minutes, or until fork tender.
Transfer the vegetables to a serving platter and enjoy. These vegetables are delicious garnished with a sprinkle of minced parsley, grated parmesan, flakey sea salt, or balsamic glaze– all optional!