Preheat your oven to 425°F (220°C).
Wash the sweet potato thoroughly. Dice it into 1/2-inch cubes for even roasting.
In a bowl, toss the diced sweet potatoes with the olive oil, a pinch of salt, pepper, and half of the garlic powder.
Spread the sweet potatoes on a baking sheet in a single layer and roast for 20-25 minutes until crispy and tender, stirring halfway through.
While the sweet potatoes roast, prepare the chicken. In a separate bowl, mix lemon juice, chopped rosemary, thyme, the remaining garlic powder, salt, and pepper.
Coat the 5 oz chicken breast with the lemon-herb marinade, ensuring it is evenly coated.
Heat a non-stick skillet over medium-high heat. Sear the chicken breast for 2-3 minutes on each side until golden.
Once seared, transfer the chicken to the oven (or cover the skillet and cook on low heat) and bake for 8-10 minutes until fully cooked and the internal temperature reaches 165°F (74°C).
Remove both the chicken and the sweet potatoes from the oven. Slice the chicken if desired and plate alongside the crispy roasted sweet potatoes.
Serve warm, garnished with a final sprinkle of fresh herbs if desired.