Preheat the oven to 375°F (190°C).
In a medium bowl, whisk together the eggs, whole milk, salt, and black pepper until well combined.
Heat the olive oil in a large skillet over medium heat. Add the breakfast sausage, breaking it apart with a spatula, and cook until browned and cooked through, about 6-8 minutes.
Add the diced onion and green bell pepper to the skillet with the sausage and cook until softened, about 4 minutes.
Pour the egg mixture into the skillet with the sausage and vegetables. Cook, stirring gently, until the eggs are scrambled and just set, about 3-4 minutes. Remove from heat.
Spread 1/2 cup of the red enchilada sauce evenly over the bottom of a 9×13-inch baking dish.
Warm the tortillas slightly to make them pliable. Spoon about 1/4 cup of the egg and sausage mixture onto each tortilla, sprinkle with 2 tablespoons of shredded cheddar cheese, then roll up tightly.
Place each rolled tortilla seam-side down in the prepared baking dish.
Pour the remaining red enchilada sauce evenly over the rolled tortillas.
Sprinkle the remaining shredded cheddar cheese evenly over the top.
Bake uncovered for 15 minutes, or until the cheese is melted and bubbly.
Remove from the oven and garnish with chopped fresh cilantro before serving.