Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Peel the sweet potato and cut it into 1/2-inch cubes; slice the chicken breast into even 1-inch strips.
Place the chicken and sweet potatoes on the prepared baking sheet and drizzle with 1 teaspoon of olive oil.
Sprinkle with sea salt, black pepper, garlic powder, and dried oregano, then toss thoroughly to coat every piece.
Spread the mixture in a single layer and roast for 20 to 25 minutes until the chicken is cooked through and the sweet potatoes are golden and tender.
While the chicken roasts, remove the tough stems from the kale and finely chop the leaves.
In a large bowl, combine the kale with the remaining 1 teaspoon of olive oil and the lemon juice, then massage the leaves with your hands for 1-2 minutes until they become dark green and tender.
Add the warm roasted chicken and sweet potatoes to the bowl with the kale, toss gently to combine, and serve immediately.