Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Dice the Yukon gold potato into 1/2-inch cubes and trim the ends off the green beans.
In a small bowl, whisk together the olive oil, rosemary, garlic powder, sea salt, black pepper, and lemon zest.
Place the diced potatoes in a bowl and toss with one-third of the herb-oil mixture until well coated.
Spread the potatoes onto the prepared baking sheet and roast for 10 minutes.
While potatoes roast, rub the remaining herb-oil mixture over the chicken breast.
Remove the baking sheet from the oven, push the potatoes to one side, and place the chicken breast and green beans on the other side.
Return the sheet to the oven and roast for 18-22 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are golden brown.
Drizzle the fresh lemon juice over the chicken and vegetables immediately before serving for a bright, fresh finish.