Preheat oven to 425°F. Line a baking sheet with parchment paper.
Toss Brussels sprouts with olive oil, salt, and pepper in a large bowl. Spread them cut-side down on the parchment-lined baking sheet.
Roast for 20–25 minutes, or until crispy and golden brown, flipping halfway through.
Make the Sudachi Ponzu Glaze: In a small saucepan over medium heat, combine Marukan Sudachi Ponzu, maple syrup, soy sauce, garlic, and ginger. Bring to a simmer and cook for 2 minutes. Stir in the cornstarch slurry (1 tablespoon cornstarch mixed with 2 tablespoons water) and whisk until thickened, about 1–2 minutes. Remove from heat.
Transfer roasted Brussels sprouts to a serving bowl. Drizzle with the Sudachi Ponzu glaze and toss to coat. Sprinkle pomegranate seeds on top.