Preheat the oven to 400F.
Add the kale to the sheet pan, drizzle with 1 tablespoon olive oil, sprinkle with ⅛ teaspoon salt, and toss to combine.
Roast for 10 minutes, tossing mid-way through, until crisp and lightly browned. Set aside.
To the same pan, add the sweet potatoes and chicken. Add 2 tablespoons olive oil, ¼ teaspoon salt, and the Italian seasoning, tossing to combine.
Spread into an even layer and roast for 30 minutes, tossing mid-way through, or until the chicken and sweet potatoes are golden and cooked through.
Serve the chicken, sweet potatoes, and kale with additional salt and a squeeze of lemon if desired.