Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper for easy cleanup.
Peel and cube the sweet potato into 1/2-inch pieces, and slice the chicken breast into even, bite-sized strips.
In a mixing bowl, toss the chicken and sweet potato cubes with 0.5 tbsp of the olive oil, sea salt, black pepper, garlic powder, and smoked paprika until thoroughly coated.
Spread the chicken and potatoes in a single layer on the prepared baking sheet, ensuring they aren't crowded so they roast rather than steam.
Roast for 20-25 minutes, flipping halfway through, until the chicken is cooked through and the sweet potatoes are tender and browned on the edges.
While the tray roasts, whisk together the remaining 0.25 tbsp of olive oil and the lemon juice in a large salad bowl.
Add the baby arugula to the bowl and toss gently to coat the leaves with the lemon dressing.
Top the arugula with the warm roasted chicken and sweet potatoes, sprinkle with raw pumpkin seeds, and serve immediately.