Preheat oven to 425 degrees.
In a large bowl, toss broccoli florets and sliced onions with 2 tablespoons oil, coriander, cumin, ½ teaspoon salt and 1 teaspoon paprika.
In a separate bowl, combine shrimp, garlic, cherry tomatoes, remaining 2 tablespoons oil, lemon zest, remaining ½ teaspoon salt and Sriracha sauce.
Spread broccoli in a single layer on a baking sheet. Roast for 10 minutes.
Add shrimp mixture to baking sheet and toss with broccoli. Roast, tossing once halfway through, until shrimp are just opaque and broccoli is tender and golden around edges, about 10 minutes more.
Serve over rice or quinoa with lemon wedges, or squeeze lemon juice all over shrimp and broccoli just before serving.
Garnish with cilantro and avocado slices.