Heat oil in a skillet, then add cubed sweet potatoes and cook for about 8 minutes until almost tender. Stir in the chopped onion and diced red bell pepper, season with salt and pepper, and cook for 3 more minutes until the vegetables are tender. Transfer this vegetable mixture to a casserole dish.

In the same skillet, brown the ground sausage over medium-high heat for about 5 minutes, breaking it apart with a spoon. Transfer the browned sausage to the casserole dish.

In a medium bowl, whisk together the eggs, almond milk, and spices. Pour this mixture over the vegetables and sausage in the casserole dish, and stir to combine.

Bake the casserole, covered with aluminum foil, in a 375°F preheated oven for 20 minutes. Remove the foil and bake for an additional 15 minutes until the top starts to brown, then let it rest for 5 minutes before serving, optionally sprinkled with green onions.