Preheat your oven to 400°F (200°C). Toss sweet potatoes and red bell peppers with olive oil, sea salt, and black pepper, then roast for 20-25 minutes until tender.

Reduce the oven temperature to 375°F (190°C). Grease a 9x13-inch baking dish with olive oil or cooking spray.

In a large skillet, heat olive oil over medium heat. Add breakfast sausage and diced onion, cooking until browned, about 5-7 minutes.

Add minced garlic and chopped Swiss chard to the skillet. Cook for another 3-4 minutes until the greens are wilted.

Transfer roasted sweet potatoes and bell peppers into the skillet with the sausage and Swiss chard mixture. Mix until well combined.

In a large bowl, whisk together eggs, milk, grated cheese, sea salt, and black pepper. Pour the egg mixture over the veggie and sausage layer in the baking dish.

Bake in the preheated oven for 25-30 minutes until golden brown on top. Check for doneness with a knife.

Allow the casserole to cool for about 5-10 minutes before slicing into squares for serving.