Whisk together the eggs, milk, salt and pepper. In a 12-inch nonstick skillet (you can use the same one you used for the potatoes, just transfer the potatoes to a plate and use the skillet as is - no need to wash), heat the oil over medium heat and add the whisked eggs mixture. Cook the eggs over medium heat, stirring often, until soft and scrambled. Remove to a plate.
Set the skillet over medium heat again and add the sausage, 1/4 teaspoon salt and a pinch of pepper. Cook the sausage, crumbling into bite-sized pieces with a spoon, until no longer pink and cooked through. Drain the grease, if needed (I like to use lean turkey sausage that doesn't have a lot of excess grease). Add the potatoes and eggs back to the skillet along with the spinach. Cook for 1-2 minutes until heated through.
Add the cheese and stir until heated through and melted. Add salt and pepper to taste!
Spoon the egg mixture into the burritos and roll up burrito-style. Serve immediately with salsa, if desired, or wrap individually in plastic and refrigerate or freeze for an easy breakfast or dinner!
Notes
Sausage: I like to use lean turkey sausage here but any type of sausage (the cook and crumble kind) can be used interchangeably based on preference. Make Ahead:these burritos can be made ahead and wrapped individually in plastic wrap, stored in the refrigerator or freezer and warmed through as needed.