Preheat your oven to 425°F (220°C) and line a large baking sheet with parchment paper for easy cleanup.
Prepare the vegetables by dicing the sweet potato into 1/2-inch cubes and chopping the broccoli into uniform bite-sized florets.
Pat the chicken breast completely dry with a paper towel; this is the secret to achieving that perfectly crispy skin.
In a large mixing bowl, toss the sweet potato cubes and broccoli florets with 0.5 tablespoon of olive oil, half of the sea salt, and half of the black pepper.
In a small ramekin, combine the remaining 0.5 tablespoon of olive oil with the dried rosemary, minced garlic, and the zest of half a lemon.
Rub the herb oil mixture thoroughly over the chicken breast, ensuring it is well-coated under and over the skin.
Spread the seasoned vegetables onto the baking sheet and place the chicken breast in the center, ensuring nothing is overcrowded.
Roast for 20 to 25 minutes, or until the chicken's internal temperature reaches 165°F and the sweet potatoes are fork-tender with caramelized edges.
Remove from the oven and squeeze the fresh lemon juice over the entire tray before serving to brighten all the flavors.