Preheat your oven to 425°F (220°C). This high heat helps the chicken skin crisp and the sweet potatoes caramelize beautifully.
In a large bowl, whisk together 2 tablespoons of olive oil, lemon zest, lemon juice, minced garlic, thyme, oregano, paprika, salt, and pepper to create the marinade.
Pat the chicken thighs dry with paper towels. Toss them in the marinade, making sure every piece is coated. Let them sit for 5–10 minutes while you prepare the potatoes.
Spread the cubed sweet potatoes on a rimmed baking sheet. Drizzle with the remaining tablespoon of olive oil and season lightly with salt and pepper. Toss to coat.
Nestle the marinated chicken thighs among the potatoes. If you like, tuck a few rosemary sprigs around for extra fragrance.
Roast in the oven for 25–30 minutes, then switch the oven to broil for 2–4 minutes to achieve extra crisp skin if desired. The internal temperature should reach 165°F (74°C).
Remove from the oven and let rest for 5 minutes. Spoon any pan juices over the chicken and potatoes to finish with a glossy, flavorful finish.