Preheat your oven to 400°F and line a large rimmed baking sheet with parchment paper for easy cleanup.
Dice the chicken breast and sweet potato into uniform 1-inch cubes, and trim and halve the Brussels sprouts.
In a large mixing bowl, toss the chicken, sweet potatoes, and Brussels sprouts with olive oil, sea salt, black pepper, garlic powder, and dried rosemary until thoroughly coated.
Spread the mixture in a single layer on the prepared baking sheet and roast for 20-25 minutes until the chicken is cooked through and the potatoes are fork-tender.
While the harvest mix roasts, place the kale in a bowl with the lemon juice and a pinch of salt, massaging the leaves with your hands for 1-2 minutes until they soften and turn a vibrant dark green.
Divide the massaged kale into serving bowls and top with the warm roasted chicken and vegetable mixture.