Heat the oven to 450°F and set a large rimmed sheet pan in the oven for 5 minutes.
Toss the shrimp and dried pepper-and-onion blend with the fajita seasoning, olive oil, salt and black pepper.
Spread the mixture carefully across the hot pan in one layer.
Roast for 8 minutes, then turn the shrimp and vegetables.
Wrap the tortillas in foil, set the packet on one corner of the pan and roast for 4 to 6 minutes more, until the shrimp are opaque and reach 145°F.
Fill the warm tortillas with the shrimp and peppers immediately.