Preheat the oven to 400°F.
Place sweet potatoes, onion, bell peppers, and mushrooms on 2 large baking sheets and drizzle with olive oil.
Sprinkle with Herbes de Provence and stir well to combine.
Season with salt and pepper.
Roast in preheated oven for 30 minutes.
Add kale to baking sheets, tossing to combine with olive oil (drizzle with a little more, if needed) and roast another 10 minutes.
Once veggies are roasted, reduce oven temperature to 350 degrees F.
Lightly grease a 9 X 13 baking dish or equally large casserole dish.
Toss together the vegetables with the bread cubes.
Place bread/veggie mixture in baking dish.
Whisk together the milk, eggs, and 1 ½ cups of the cheese. Pour it over the bread and veggies.
Sprinkle the top with the remaining cheese and bake for 45-50 minutes, until top is golden and center is set.
Serve and enjoy!
*Note: You can roast the vegetables a day in advance. You can also prepare the entire strata a day in advance, you will just need to add ~10 minutes to the baking time if you put it in the oven straight from the refrigerator.