Preheat oven to 425℉.
On a large sheet pan toss together shrimp, bell pepper, onion, oil, chili powder, cumin, oregano, and salt. Roast until the shrimp are opaque and vegetables are just tender, about 10 minutes.
Serve vegetables and shrimp with tortillas. If desired, top with sour cream, cilantro, and/or green onion.