Cut off the brown ends of the Brussels sprouts and pull off any yellow outer leaves. Cut them in half lengthwise.
Mix the oil, miso paste, maple syrup, vinegar, tamari and Sriracha together in a large bowl. Remove about 1 tablespoon of the sauce and save it to toss with the Brussels sprouts later. Add the Brussels sprouts to the bowl and toss to coat them with the sauce. Transfer the Brussels sprouts to a baking sheet sprayed with olive oil cooking spray and spread them out in a single layer.
Roast Brussels sprouts in the oven until caramelized and tender, 20-25 minutes. Stir them once or twice during cooking. Remove the tray from the oven and drizzle the reserved sauce on top. Toss to combine. Serve warm.