In a mixing bowl, combine the cooked chicken with ranch dressing. Stir until the chicken is well coated. Season with salt and pepper to taste.
Heat olive oil in a skillet over medium heat. Add the chicken mixture to the skillet and cook for about 5 minutes, stirring occasionally, until heated through and slightly crispy.
Lay out the flour tortillas on a clean surface. Divide the chicken mixture evenly among the tortillas, placing it in the center of each.
Top the chicken with shredded lettuce, diced tomatoes, and shredded cheddar cheese.
Fold in the sides of each tortilla and then roll it up tightly from the bottom to the top to form a wrap.
If desired, place the wraps seam-side down in the skillet and cook for an additional 2-3 minutes on each side until golden brown and crispy.
Slice each wrap in half and serve immediately.