In a large skillet over medium-high heat, cook the sausage, breaking it up, until browned. Transfer to a bowl, leaving about 1 tablespoon of fat in the pan.
Add the hash browns and bell pepper to the skillet and cook for 8–10 minutes, stirring occasionally, until the potatoes are golden. Add to the sausage.
Whisk the eggs, milk, salt, and pepper. Reduce the heat to medium-low, pour the eggs into the skillet, and gently scramble until just set. Add to the bowl and stir everything together.
Let the filling cool for 10–15 minutes.
Warm the tortillas so they’re pliable. Divide the filling and cheese among them, fold in the sides, and roll up tightly.
Wrap each burrito in parchment paper, then foil or place in freezer bags. Freeze.
To reheat: remove the foil, wrap in a damp paper towel, and microwave 1½–2½ minutes, flipping halfway, until hot in the center.