In a bowl, combine the yogurt, olive oil, chicken, garlic, paprika, oregano, chili flakes, and a large pinch each of salt and pepper. Let marinate for 15 minutes at room temperature or up to overnight in the refrigerator.Preheat the oven to 425° F. Arrange the chicken on a baking sheet. Bake 25 minutes, until cooked through. Switch the oven to broil. Broil 1-2 minutes, until the chicken chars on the edges. Thinly slice the chicken. Meanwhile, mix the lettuce, avocado, peperoncini, dill, and feta in a bowl.Place one tortilla at a time in the microwave for 20 seconds. Spread on a layer of pesto, then add the lettuce mix and the chicken. Spoon over some of the tzatziki. Fold the tortilla over the filling. Then fold the sides and ends of the tortillas over the filling and roll forward. Repeat with remaining ingredients.Serve at room temp or wrap in foil and warm in the oven. Enjoy with extra tzatziki sauce and garlic tahini, if desired.