Preheat your oven to 400°F and line a rimmed baking sheet with parchment paper.
Cut the chicken breast into 1-inch pieces and dice the yellow potato into 1/2-inch cubes.
In a medium mixing bowl, toss the chicken and potatoes with olive oil, dried oregano, garlic powder, sea salt, and black pepper until evenly coated.
Spread the chicken and potato mixture in a single layer on the prepared baking sheet.
Roast for 20 to 25 minutes, or until the chicken is cooked through and the potatoes are golden and tender.
While the chicken roasts, warm the cooked white rice in a small saucepan or microwave until steaming.
Stir half of the lemon juice into the warm rice to infuse it with citrus flavor.
Remove the tray from the oven, drizzle the remaining lemon juice over the chicken and potatoes, and garnish with chopped fresh parsley.
Plate the lemon-infused rice and top it with the roasted chicken and potatoes.