Cook rice according to package directions. (You'll want it to be cooked and hot at the same time that you're ready to serve the Brussels sprouts.)
Preheat oven to 425°F.
Line a rimmed baking sheet with parchment paper.
In a medium bowl, toss Brussels sprouts with 2 tablespoons of the peanut oil and spread in a single layer on prepared baking sheet; season with salt and freshly ground black pepper. Roast 20 minutes, until tender with crispy edges, stirring once about half way through roasting time.
Meanwhile, whisk together cornstarch and 1 teaspoon water in a small bowl until smooth.
Heat remaining 1 tablespoon peanut oil in a small saucepan over medium heat. Add garlic and ginger; cook and stir until garlic is golden brown, about 2 minutes. Add chili paste, soy sauce, honey, rice vinegar and ¼ cup water and bring to a boil; stir in cornstarch mixture. Reduce heat and simmer, stirring constantly until sauce has thickened slightly, about 2 minutes. Remove from heat.
When Brussels sprouts are done, transfer to medium bowl. Pour sauce over and toss to coat. Transfer to serving platter or divide among 4 bowls. Sprinkle with peanuts and red pepper flakes (optional); serve with hot cooked rice.
For a vegan version, skip the honey and use sugar or other sweetener instead.