Place halved brussels sprouts in a medium bowl, along with the sliced shallot, smashed garlic, and chiles (if using). In a small bowl or measuring cup, whisk together the oil and sambal oelek. Pour over the brussels sprouts mixture, and mix until vegetables are evenly coated.
Spread brussels sprout mixture in a single layer onto a baking sheet, and roast in the oven at 400 degrees until vegetables are beginning to brown nicely, about 25 minutes. Be sure to stir the vegetables once about halfway during cooking to prevent too much browning on the bottom.
While brussels sprouts are roasting, make the vinaigrette by whisking together the cilantro, lime juice, canola oil, fish sauce, brown sugar, and sriracha until smooth.
Once brussels sprouts are done roasting, cool them for about 5 minutes, then transfer them to a medium bowl. Give the vinaigrette a good stir, then pour over the roasted brussels sprouts, tossing to coat.
Transfer to a serving plate and top with more cilantro and a sprinkling of chopped peanuts. Serve immediately.