Preheat your oven to 400°F (200°C) and line a large baking sheet with parchment paper.
Slice the sweet potato into half-inch thick wedges and toss them on one side of the baking sheet with 0.5 tbsp of olive oil, a pinch of sea salt, and black pepper.
Place the chicken breast on the other side of the sheet, rubbing it with the remaining 0.5 tbsp of olive oil, dried oregano, and the remaining salt and pepper.
Roast in the oven for 20 to 25 minutes, or until the chicken reaches an internal temperature of 165°F and the sweet potatoes are tender.
While the chicken roasts, finely chop the fresh parsley and mince the garlic cloves.
Zest the entire lemon and squeeze out 1 tbsp of fresh juice into a small bowl, then stir in the parsley and garlic to create the gremolata.
Remove the tray from the oven and let the chicken rest for 5 minutes before slicing it into strips.
Top the sliced chicken generously with the fresh lemon-parsley mixture and serve immediately alongside the roasted sweet potatoes.