In a large bowl, whisk together eggs, milk, salt, and pepper until uniform and slightly frothy. Set aside.

In a large nonstick skillet over medium-high heat, cook the sausage, breaking it into small crumbles, until browned and cooked through (internal temp 160°F). Transfer to a bowl lined with paper towels to drain excess fat.

Reduce heat to medium. Add butter to the same skillet. Once melted, add onion and bell pepper. Cook, stirring occasionally, until softened and translucent, about 5 minutes.

Add the thawed hash browns to the skillet. Spread them into an even layer and let cook undisturbed for 3-4 minutes until the bottom is golden. Stir and repeat until most shreds are browned and crisp.

Pour the egg mixture over the hash browns and vegetables. Let sit for 30 seconds, then gently stir with a silicone spatula, pushing cooked eggs from the edges toward the center. Cook until the eggs are just set but still soft (they will finish cooking in the microwave later). Remove from heat immediately.

Stir the cooked sausage and shredded cheddar into the egg mixture until combined. Let cool for 10 minutes at room temperature.

Lay a tortilla on a clean work surface. Spoon about 3/4 cup of filling into a log shape across the center, leaving a 2-inch border on each side.

Fold the two sides over the filling, then roll from the bottom edge tightly, tucking as you go. Wrap each burrito tightly in aluminum foil.

Place all foil-wrapped burritos on a baking sheet and freeze for 2 hours until solid. Transfer to a labeled freezer bag, squeezing out excess air. Freeze for up to 3 months.

To reheat: Remove foil and wrap burrito in a damp paper towel. Microwave on high for 2 minutes (for one burrito), then flip and microwave another 1-2 minutes until center reaches 165°F. For a crispy exterior, finish in a dry skillet over medium heat for 1-2 minutes per side.