In a large bowl, combine 2 cups hot cooked rice, 2 cups cooked broccoli, 1 pound shredded cooked chicken, 0.5 ounce ranch seasoning, 8 ounces drained chopped water chestnuts, and 3/4 cup shredded cheddar cheese; stir until evenly mixed.
Lay a whole wheat tortilla flat and sprinkle about 1 tablespoon (¼ cup total divided among 4) shredded cheddar in the center of each tortilla.
Scoop about one quarter of the chicken and rice mixture onto each tortilla on top of the cheese, then fold in the sides and roll tightly to form a wrap.
Preheat an indoor grill pan, grill, or skillet over medium heat. Place wraps seam-side down and grill for about 4 minutes per side, or approximately 8 minutes total, until golden and heated through.
Remove from the heat, let rest 1 minute, then cut in half if desired and serve hot.