Preheat your oven to 400°F.
In a small bowl, combine the juice of the lemon, olive oil, finely chopped rosemary and thyme, salt, and pepper to create a marinade.
Place the chicken breast in a shallow dish and pour half of the marinade over it, letting it marinate for at least 15 minutes.
Peel and cube the sweet potato into uniform pieces. Toss the cubes with a little olive oil, salt, pepper, and any remaining herbs.
Arrange the marinated chicken breast and sweet potato cubes on a baking sheet lined with parchment paper.
Roast in the preheated oven for about 20-25 minutes, until the chicken reaches an internal temperature of 165°F and the sweet potatoes are tender and lightly browned.
While the chicken and potatoes are roasting, prepare a fresh salad by tossing the mixed greens with a squeeze of lemon juice and a drizzle of olive oil.
Once cooked, plate the roasted chicken along with sweet potatoes and serve on a bed of fresh greens.