Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper.
Wash and dice the Yukon Gold potato into uniform 1/2-inch cubes to ensure even roasting.
Mince the fresh garlic clove and finely chop the fresh rosemary leaves.
In a medium bowl, toss the potato cubes with half of the olive oil, half of the sea salt, and half of the black pepper.
Spread the potatoes in a single layer on the prepared baking sheet and roast for 10 minutes.
While potatoes are roasting, whisk together the remaining olive oil, lemon juice, lemon zest, minced garlic, and chopped rosemary in a small bowl.
Rub the chicken breast thoroughly with the lemon-herb mixture and the remaining salt and pepper.
Remove the baking sheet from the oven, slide the potatoes to one side, and place the chicken breast on the other side.
Return the sheet to the oven and roast for an additional 18-22 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are golden-brown.
Remove from the oven and let the chicken rest for 5 minutes to lock in the juices before slicing and serving alongside the roasted potatoes.