Preheat your oven to 425°F (220°C) and line a large rimmed baking sheet with parchment paper.
Dice the yellow potato into 1/2-inch cubes and toss them in a bowl with 0.25 tbsp of the olive oil and half of the sea salt and black pepper.
Spread the potatoes in a single layer on the prepared baking sheet and roast for 15 minutes to begin the browning process.
While the potatoes roast, whisk together 0.25 tbsp of olive oil, the lemon juice, garlic powder, and oregano in a small bowl, then brush it evenly over the chicken breast.
Toss the trimmed green beans with the remaining 0.25 tbsp of olive oil and the rest of the sea salt and black pepper.
Remove the baking sheet from the oven, push the potatoes to one side, and add the chicken breast and green beans to the other side.
Return the sheet to the oven and roast for another 18 minutes, or until the chicken reaches an internal temperature of 165°F and the potatoes are golden.
Allow the chicken to rest for 5 minutes before slicing to ensure it stays juicy, then serve alongside the crispy potatoes and tender beans.