Preheat oven to 350°F (175°C) and grease a 9x13 inch baking dish.
In a skillet, cook breakfast sausage until browned. Add diced tomatoes & green chiles. Cook for 2–3 more minutes.
In a separate pan, melt butter and cook hashbrowns until lightly golden.
In a bowl, whisk together eggs, half & half, sour cream, salt, and pepper.
Layer half the tortillas at the bottom of the baking dish.
Add layers of hashbrowns, sausage mixture, and shredded cheese. Repeat layers, ending with cheese on top.
Pour egg mixture evenly over the casserole.
Bake uncovered for 40–45 minutes until the center is set and the top is golden. Let it cool slightly before serving.