Preheat the oven to 400 degrees. Line a baking sheet with tinfoil then coat with cooking spray.
Boil the sliced potatoes in a pot of water for 5 minutes. Drain and let cool.
Place the sliced potatoes, onion, mushrooms, and broccoli on the prepared baking sheet. Place into the oven and roast for 15 minutes; add the asparagus and tomatoes then continue to roast for 10 minutes. Remove from the oven and reduce oven temperature to 350 degrees.
Place some of the roasted veggies into the bottom of the tart pan; next add a bit of the Swiss cheese. Combine the eggs with the milk then season with sea salt and freshly cracked pepper, to taste. Whisk the eggs until they are mixed thoroughly. Pour the egg mixture into the tart pan then add the remaining roasted veggie mixture and Swiss cheese to the top.
Place into the oven and bake at 350 degrees for 25-30 minutes, or until a tester inserted in the center comes out clean. Let the frittata cool for a few minutes before slicing and serving. Enjoy.