Prep a 17" x 12" sheet pan with parchment paper (my favorite), aluminum foil or just regular spray oil.
Preheat oven to 400 degrees.
For the seasoning: in a small bowl, whisk together chili powder, cumin, paprika, salt, and pepper. Set aside.
Slice peppers, onions and mushrooms. Place on the sheet pan.
If you are using fresh chicken (or if you are using plant-based Chik'n), place in a bowl. Add garlic, half of your oil, and half of the seasoning mixture, then stir together to coat the chicken.
Layer the seasoned and coated chicken on top of the vegetables in a single layer. If you are using pre-cooked Chick'n strips or plant-based coated chicken, wait to add to the sheet pan until the last fifteen minutes of baking as it is precooked.
After oven has preheated, roast the veggies and chicken, tossing halfway through. Bake until vegetables are fully cooked, about 20-25 minutes. If you used raw chicken, be sure it reaches 165 degrees in the center.
Warm tortillas by wrapping them tightly in aluminum foil and placing them in the warm oven for a few minutes.