Preheat oven to 400°F (200°C). Line a large sheet pan with parchment paper or foil.
Add meat, bell peppers, and onion to the sheet pan. Drizzle with olive oil and sprinkle with taco seasoning, salt, and pepper.
Toss everything together and spread into an even layer.
Roast for 15–20 minutes, stirring halfway through, until meat is cooked and vegetables are tender with lightly crispy edges.
Warm tortillas in the oven during the last 5 minutes or in a skillet.
Spoon filling into tortillas and add desired toppings. Serve immediately.