Start by making Oven Roasted Vegetables one day and save out 1/3 of the recipe to make this frittata.
Roasted Vegetable Frittata
Preheat oven to 350°F.
Break the eggs into a medium bowl. Add milk and whisk until mixture is very well combined. Season with salt and freshly ground black pepper.
Heat a 10-inch, well seasoned, cast iron skillet over medium high heat until hot. Add the oil to the pan and swirl to coat. Arrange 1/3 recipe of leftover vegetable bake in a single layer; pour egg mixture over all. Stir gently to allow egg to flow under vegetables. Remove from heat and sprinkle with cheese.
Bake for 25-35 minutes, until the frittata has puffed and the center is set. Allow to cool for 10 minutes before slicing in to wedges. Serve warm.