Preheat oven to 400°F (200°C); line a baking sheet with parchment paper.
In a bowl, whisk maple syrup, soy sauce, garlic, smoked paprika, and olive oil.
Toss vegan chicken in the marinade; let it sit 10 minutes for flavor infusion.
Arrange Brussel sprouts on the sheet; drizzle with olive oil, season with salt, pepper, and optional chili flakes.
Place vegan chicken beside sprouts; roast 25–30 minutes, flipping halfway, until crispy and caramelized.
Serve hot, drizzle remaining glaze over the top, and enjoy immediately.