Preheat oven to 425°F and line a large sheet pan with parchment paper or spray with cooking spray.
In a large bowl, mix buffalo sauce and melted butter together. Add cauliflower florets and toss to coat completely.
In a separate bowl, toss chickpeas and Brussels sprouts with olive oil, garlic powder, and salt.
Arrange buffalo cauliflower, chickpeas, and Brussels sprouts on the sheet pan in a single layer, keeping them slightly separated.
Roast for 25-28 minutes, tossing everything halfway through, until cauliflower is tender and edges are crispy.
Drizzle with ranch or blue cheese dressing, top with green onions, and serve with celery sticks on the side.