Preheat oven to 425F.
Toss the broccoli with about 2 tablespoons of oil, the cumin, coriander, 1/4 teaspoon of the chili flakes, and half the salt and pepper. In a small bowl, toss the shrimp with the remaining chili flakes, salt and pepper, olive oil and the lemon zest. Cut the lemon lengthwise into quarters.
Spread the broccoli out on a parchment-lined rimmed baking sheet, add the lemon wedges if you like, and roast for 10 minutes. Add the shrimp and cook for 8-10 minutes more – just until the shrimp are opaque. Serve over rice, with a squeeze of lemon.