Winter Vegetable Frittata

Heat oven to 400F. Line baking sheet with aluminum foil.
On baking sheet, toss brussels sprouts and leek with 1 tablespoon olive oil. Scatter them onto prepared baking sheet. Roast until deep golden brown, around 30 minutes. When those are done, turn oven heat down to 375F.
While brussels sprouts and leek are roasting, heat 2 teaspoons olive oil in 10-inch nonstick oven-safe saute pan over medium heat. Add kale; saute until kale is tender, around 6 minutes. Remove kale from pan and set aside. Wipe pan with paper towel.
Slice sweet potato very thinly. Toss slices with 2 teaspoons olive oil to coat. Arrange sweet potato slices in pan one at a time, fanning over each other to completely cover the bottom of the pan.
Place another pan of the same size, or a pie plate, on top of the sweet potatoes to weigh them down. Cook for 5 minutes on medium-high heat, then turn to medium heat and cook for about 15 minutes, until soft.
While sweet potato crust cooks, lightly beat eggs in large bowl. Season with salt and pepper. Stir in rosemary, kale, brussels sprouts, and leeks.
Remove top pan from potatoes and pour in the egg mixture. Scatter goat cheese on top.
Bake in oven until slightly puffed, golden, and center is slightly set, 18 to 20 minutes. Gently run a spatula around edges and bottom of frittata to loosen. Slice into wedges and serve.