Preheat your oven to 400°F (200°C) and line a large rimmed baking sheet with parchment paper for easy cleanup.
Scrub the sweet potato thoroughly and slice it into 1/2-inch thick wedges.
Place the sweet potato wedges on the baking sheet, drizzle with 0.5 tbsp of olive oil and a pinch of sea salt, then roast for 15 minutes.
While the potatoes roast, pat the ocean perch fillets dry with a paper towel and season both sides with garlic powder, dried oregano, salt, and pepper.
Remove the baking sheet from the oven, push the potatoes to one side, and place the perch fillets and trimmed asparagus on the other side.
Drizzle the remaining 0.5 tbsp of olive oil over the fish and asparagus, and place thin slices of lemon directly on top of the perch.
Return the pan to the oven and roast for another 10-12 minutes until the fish is opaque and flakes easily with a fork.
Garnish the entire dish with freshly chopped parsley and serve immediately while hot.