Heat the oven to 450° F and position the middle rack.
Mix all of the seasoning ingredients together in a small bowl; set aside.
Prepare the shrimp. Peel, devein, and remove the tails if you need to. Then, rinse the shrimp under cold water and gently pat them dry; set aside.
Place the peppers and onions into a large bowl. Drizzle them with a bit of olive oil, then sprinkle with 3/4 of the seasoning, leaving a bit for the shrimp. Toss to coat, and spread them out on half of the sheet pan.
Transfer the shrimp to the bowl where you seasoned the vegetables. Sprinkle the rest of the seasoning over the shrimp, toss to coat, then spread them out on the other half of the sheet pan. (You could toss the shrimp and vegetables together, but I like to keep them separate. It makes filling the tortilla with my preferred ratio of veggies to shrimp easier. It's a personal thing!)
Place in the oven and bake for 8-10 minutes.
Remove the pan from the oven and serve fajitas with flour tortillas, lime wedges, and your choice of garnishes and condiments.