Preheat oven to 400 degrees F.

In a large bowl, add sliced bell pepper and onion. Drizzle in 2 tablespoons olive oil. Sprinkle with 1 tablespoon fajita spice blend and toss to evenly combine.

Add onion and pepper mixture to a large sheetpan and roast in preheated oven for 15 minutes.

Meanwhile, add prepared shrimp to the same bowl used for the veggies. Add 1 tablespoon olive oil and remaining 1 tablespoon fajita spice blend. Toss to evenly combine.

After first 15 minutes, pull the sheetpan from the oven and use tongs to toss the peppers and onions. Evenly spread the raw, coated shrimp on the sheetpan and return to the oven for 6 to 8 minutes, until shrimp is cooked to an internal temperature of 140 degrees F.

Remove and garnish with chopped onions and lime slices to serve.