Preheat your oven to 400°F (200°C).
Slice the sweet potato into 1/2-inch rounds or cubes for even roasting and toss them with a drizzle of olive oil, a pinch of salt, and black pepper.
Place the sweet potatoes on a baking sheet and roast for about 15 minutes while you prepare the chicken.
In a small bowl, combine the juice and zest of the lemon, minced garlic, dried thyme, dried rosemary, a pinch of salt, and a pinch of black pepper.
Place the chicken breast on a separate baking tray. Rub the lemon-herb mixture evenly over the chicken.
After the sweet potatoes have roasted for 15 minutes, add the chicken to the oven and continue roasting both the chicken and sweet potatoes for an additional 18-20 minutes, or until the chicken is cooked through and the sweet potatoes are tender and slightly caramelized.
Once done, let the chicken rest for a few minutes before slicing. Serve the sliced chicken alongside the roasted sweet potatoes, garnished with any extra lemon zest if desired.