Preheat oven to 400°F. On a baking sheet, add potatoes with oil, ½ tbsp of garlic, ½ tsp salt, and ½ tsp black pepper. Roast for 15 minutes.
Remove baking sheet. Spread potatoes to one side and place salmon fillets on the other side. Rub with remaining garlic, and parsley. Add in asparagus on another side or pan.
In a bowl, combine lemon juice and melted butter. Pour over salmon and asparagus, continue to season with remaining salt and pepper.
Return sheet to oven and continue baking for 10 minutes.
Serve with lemon slices.