Preheat oven to 350°F (175°C). Lightly grease a 9x13-inch baking dish.
In a large bowl, mix together the shredded chicken, 1 cup of cheddar cheese, cream of chicken soup, sour cream, milk, Ro-Tel, and taco seasoning.
Layer half of the crushed Doritos in the bottom of the baking dish.
Spread the chicken mixture over the Doritos layer.
Top with the remaining crushed Doritos and sprinkle with the remaining 1 cup of cheese.
Bake for 25–30 minutes, until hot and bubbly. Garnish with green onions, if desired. Serve warm.