Preheat oven to 450 degrees and line a baking sheet with parchment paper. In a large bowl, toss Brussels sprouts with 2 Tbsp olive oil, salt, and a turn of freshly ground black pepper. Transfer to prepared baking sheet and spread out into a single layer. Roast for 20 to 25 minutes, tossing halfway through, or until browned on most sides.
Meanwhile, combine honey, buffalo sauce, and butter in a small saucepan and cook over medium heat, whisking constantly, until the butter has melted and the glaze has thickened slightly, about 3 minutes.
When Brussels sprouts are done, transfer to a large mixing bowl and toss in the glaze until completely coated with the glaze. Taste and add more salt or pepper, if needed.
Transfer to a serving dish and garnish with scallion slices and lemon zest (if using). Serve right away.