01 - Preheat the oven to 425°F. Line a large sheet pan with parchment paper.
02 - In a bowl, toss the chicken pieces with olive oil, smoked paprika, garlic powder, oregano, salt, pepper, and lemon juice until evenly coated.
03 - Arrange the seasoned chicken pieces on one half of the prepared sheet pan in a single layer.
04 - In a separate bowl, toss the red onion, bell peppers, and cherry tomatoes with olive oil, salt, and pepper.
05 - Spread the seasoned vegetables on the other half of the sheet pan, keeping them separate from the chicken.
06 - Roast for 20 to 25 minutes, stirring halfway through cooking, until the chicken is cooked through and vegetables are tender with slight charring.
07 - While chicken and vegetables roast, whisk together mayonnaise, Greek yogurt, parsley, dill, chives, garlic, lemon juice, onion powder, salt, and black pepper in a bowl until smooth and well combined.
08 - Warm the pita breads in the oven for a few minutes or in a dry skillet until pliable.
09 - Fill each warmed pita with shredded lettuce, roasted chicken, vegetables, a generous drizzle of herby ranch sauce, and a sprinkle of feta cheese if desired. Serve immediately.