Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel and cube the sweet potato into 1/2-inch pieces. Slice the chicken breast into even 1-inch strips.
Place the chicken and sweet potatoes on the baking sheet. Drizzle with half of the olive oil and season with sea salt, black pepper, garlic powder, and dried oregano. Toss well to coat.
Roast in the oven for 20-25 minutes, flipping halfway through, until the chicken is cooked through and the sweet potatoes are tender and caramelized.
While the chicken and potatoes roast, remove the tough ribs from the kale and chop the leaves into bite-sized pieces. Place in a large bowl.
In a small jar or bowl, whisk together the remaining olive oil, lemon juice, and Dijon mustard to create the dressing.
Pour half of the dressing over the kale and use your hands to massage the leaves for 1-2 minutes until they become dark green and tender.
Assemble the bowl by topping the massaged kale with the roasted chicken and sweet potatoes. Drizzle with the remaining dressing and serve immediately.