Preheat oven to 425°F (220°C). Line a large rimmed baking sheet with parchment paper.
Rinse Brussels sprouts and pat completely dry. Trim stem ends, remove any damaged leaves, and cut in half lengthwise.
In a large bowl, toss Brussels sprouts with avocado oil, salt, and black pepper until evenly coated.
Arrange Brussels sprouts cut-side down in a single layer on the prepared baking sheet, making sure not to overcrowd.
Roast for 22-25 minutes, without stirring, until deeply golden brown on the bottom with crispy edges and tender centers.
While Brussels sprouts roast, make the glaze: In a small saucepan over medium heat, combine coconut aminos, rice vinegar, maple syrup, sesame oil, garlic, ginger, and red pepper flakes (if using). Whisk together and bring to a gentle simmer. Cook for 3-4 minutes, stirring occasionally, until slightly thickened and glossy. Remove from heat.
Transfer hot roasted Brussels sprouts to a large mixing bowl. Pour the warm glaze over them and toss gently until all sprouts are well coated.
Transfer to a serving platter or bowl. Garnish with sliced green onions, toasted sesame seeds, and cilantro if using. Serve immediately.
