Preheat oven to 425 degrees. Place pecans on a baking sheet and roast for 8 minutes, or until fragrant. Set aside to cool.
Toss brussels sprouts with oil, salt, and pepper. Place on a baking sheet, cut side down. Roast for 15 to 20 minutes or until golden brown and crispy.
In this time, make the dressing. Whish maple syrup, miso paste, vinegar, and mustard together until smooth. Slowly drizzle oil in, making sure its thick and emulsified. Season with salt and pepper.
Transfer brussels to a plate and drizzle the dressing over. Sprinkle on your toasted pecans.