Preheat oven to 200 degrees Celsius (400 degrees Fahrenheit).
On a large rimmed baking sheet, toss the halved baby potatoes with 1 tablespoon of olive oil, half the salt, and half the pepper.
Roast the potatoes in the preheated oven for 15 minutes.
Remove the tray from the oven and move the potatoes to the outer edges.
Place the salmon fillets and asparagus spears in the center of the tray.
Drizzle the salmon and asparagus with the remaining olive oil, then sprinkle with minced garlic, oregano, and the remaining salt and pepper.
Place lemon slices on top of each salmon fillet.
Return the tray to the oven and roast for an additional 10 to 12 minutes until the salmon is cooked through and the asparagus is tender.
Garnish with fresh dill before serving.