Cook Sausage: In a large skillet over medium heat, cook breakfast sausage until browned and crumbled. Do not drain fat.
Make Gravy: Sprinkle flour over sausage and stir for 1 minute. Gradually whisk in milk until smooth. Add garlic powder, salt, and pepper. Simmer 5 minutes until thickened.
Scramble Eggs: In another skillet, melt butter over low heat. Beat eggs with milk, salt, and pepper. Scramble gently until just set. Remove from heat.
Assemble: Preheat oven to 350°F. Grease a 9×13 inch baking dish. Fill each tortilla with scrambled eggs and both cheeses. Roll tightly and place seam-down in dish.
Bake: Pour warm gravy over enchiladas. Cover with foil and bake 20-25 minutes until heated through.
Serve: Sprinkle with green onions. Let rest 5 minutes before serving with breakfast potatoes.