01 - Preheat oven to 400°F. Lightly grease a baking dish with olive oil or cooking spray.
02 - In a large bowl, combine the sliced bell peppers and red onion with olive oil, chili powder, smoked paprika, cumin, garlic powder, onion powder, salt, and black pepper. Toss until evenly coated.
03 - Slice each chicken breast horizontally through the center without cutting all the way through to create a butterflied cutlet. Place between plastic wrap and pound to approximately 1/4 inch thickness using a meat mallet or rolling pin.
04 - Divide the seasoned vegetable mixture and shredded Monterey Jack cheese evenly among the flattened chicken cutlets. Lay the filling across the center of each piece, then roll up tightly and secure with toothpicks.
05 - Place the chicken roll-ups seam-side down in the prepared baking dish. Sprinkle any remaining fajita seasoning over the top.
06 - Bake for 25 to 30 minutes until the chicken is cooked through (internal temperature reaches 165°F) and the cheese is bubbling and golden.
07 - Remove toothpicks from each roll-up. Garnish with chopped fresh cilantro and serve alongside lime wedges and sour cream if desired.