1. Preheat oven to 325 degrees F. Spray a 15x10-inch baking pan with cooking spray. Line with a piece of parchment or wax paper. Spray paper with additional cooking spray.
2. Beat eggs, milk, flour, green onion, salt and pepper into large bowl with a wire whisk until well blended.
3. Carefully pour into pan. Bake for 20 minutes or until eggs are set.
4. Cook sausage and mushrooms in a large skillet over medium heat for 4-5 minutes or until mushrooms are tender. Stir in spinach: cook and stir until spinach is wilted.
5. Loosen eggs from sides of pan and carefully invert onto another piece of parchment or waxed paper. Top with sausage mixture and 3/4 cup cheese. Roll-up.
6. Place on back on baking pan. Top with remaining 1/4 cup cheese. Bake for 5 minutes or until cheese is melted. Cut into slices.