Preheat your oven to 400°F (200°C).
Prepare the potatoes: Toss the cubed potatoes with 1½ tablespoons of olive oil, half the garlic, half the salt, half the pepper, and half the herbs. Spread on a large baking sheet.
Roast the potatoes for 15 minutes.
Season the salmon and asparagus: While the potatoes roast, brush the salmon fillets and asparagus with the remaining olive oil. Sprinkle with the remaining garlic, salt, pepper, and herbs.
Add to the sheet: After 15 minutes, push the potatoes to one side. Add the salmon and asparagus. Place lemon slices over the salmon.
Roast everything together for another 12–15 minutes, until the salmon is cooked through and the asparagus is tender.
Garnish and serve: Finish with a sprinkle of fresh parsley or basil just before serving..