Preheat the oven to 400°F (204°C). In a large bowl, toss the Brussels sprouts with the olive oil, garlic powder, red pepper flakes, salt, and pepper. Add the Brussels sprouts to a large baking sheet cut side down. Roast for about 10 minutes.
Remove sheet pan from oven and add chopped garlic. Return to oven and cook an additional 10-12 minutes or until sprouts are a little darker than golden brown and tender.
While Brussels are cooking, in a medium bowl, make peanut sauce by whisking together until well combined the peanut butter, soy sauce, rice vinegar, maple syrup, lime juice, chili garlic sauce, garlic and ginger. Use warm water, 1 tablespoon at a time, until dressing like consistency is reached. Set aside.
In a large pot over high heat, bring 4 cups water to boil. Add edamame and return to boil. Cook for 4 minutes, stirring occasionally. Drain edamame. Into the same pot, add green onions, sesame seeds, garlic powder, salt and pepper. Stir together well. Drizzle sesame oil, if adding, and toss until well combined.
When Brussels are done cooking, return to large bowl and drizzle balsamic vinegar over and gently toss to combine.
To serve, add Brussels and edamame to a dish and toss together gently. Drizzle with peanut sauce. Top with more green onions and sesame seeds if desired.