Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Peel the sweet potato and cut it into uniform 1-inch cubes.
Toss the sweet potato cubes with 0.25 tablespoons of olive oil and a pinch of sea salt directly on the baking sheet.
In a small ramekin, mix together the dried rosemary, thyme, garlic powder, sea salt, and black pepper.
Pat the chicken breast dry with a paper towel, rub with the remaining 0.5 tablespoons of olive oil, and coat evenly with the herb spice blend.
Place the chicken on the baking sheet next to the sweet potatoes and roast for 25 to 30 minutes, or until the chicken reaches an internal temperature of 165°F.
While the chicken and potatoes roast, steam the broccoli florets in a steamer basket for 4 to 5 minutes until they are vibrant green and tender.
Allow the chicken to rest for 5 minutes before slicing, then plate with the roasted potatoes and steamed broccoli, finishing with a fresh squeeze of lemon juice.