Preheat your oven to 400F/200C and get a 9x13 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 18-20 minutes, or until the bacon is done. The bacon will be done first, so keep an eye on it and remove it from the oven when it's done, and place on paper towels to dry. 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 4-5 minutes. Add the minced garlic and saute another 30 seconds. Transfer the onion and bell pepper to the casserole pan.
Remove the sweet potato from the oven and add it to the casserole pan, with the crumbled bacon, onion, and bell pepper. If you'd like to add cheese, you can add it to the casserole pan now.
Stir all of the ingredients in the casserole pan together. Feel free to season with more salt and pepper.
In a mixing bowl, stir the eggs with the milk.
Pour the egg mixture on top of the meat and vegetables. Cook for 25-30 minutes, or until the center is cooked through and the edges are slightly golden. You can test the center with a toothpick.
If you'd like, garnish the breakfast casserole with green onion, or herbs. Then serve warm with sliced avocado, toast, or a side salad.