Preheat your oven to 400°F (200°C) and get a 9x13-inch casserole pan out. On one baking sheet pan, toss the diced sweet potato with olive oil, garlic powder, paprika, cumin, salt, and pepper. Set aside.
On another sheet pan, add slices of bacon. Then place both the sweet potato and bacon in the oven and cook for 15 to 20 minutes, or until the bacon is crispy. The bacon will be done first, so keep an eye on it and remove it from the oven when it's done, then place it on a paper towel-lined plate. Stir the sweet potato and continue cooking it for another 15 minutes.
While the sweet potato is cooking, cook the breakfast sausage in a pan on medium-high heat. Once it's browned, remove it with a slotted spoon and place it in the casserole pan.
Drain off all but a tablespoon of grease from the pan, then saute the onion and bell pepper for 4 to 5 minutes. Add the minced garlic and saute for another minute. Transfer this mixture to the casserole pan.
Remove the sweet potato from the oven and add it to the casserole pan along with the crumbled bacon, breakfast sausage, onion, and bell pepper. If you'd like to add cheese, you can add it to the casserole pan now or sprinkle it on top.
Stir all of the ingredients in the casserole pan together. Feel free to season with more salt and pepper.
In a mixing bowl, whisk the eggs and milk together, until lightly frothy.
Pour the egg mixture on top of the meat and vegetables. Cook for 25 to 30 minutes, or until the center is cooked through and the edges are slightly golden.
Slice the breakfast casserole into squares, and if you'd like, garnish with green onion or herbs before serving.