Preheat the oven to 400°F (200°C).
Toss the halved potatoes with 1 tablespoon of olive oil, salt, and pepper, and spread them on a sheet pan in a single layer.
Roast for 20 minutes, until starting to turn golden and easily pierced with a fork.
Push the potatoes to one side of the pan and add the salmon fillets to the empty space.
Drizzle the salmon with the remaining olive oil and sprinkle with the rosemary or thyme, minced garlic, salt, and pepper.
Top each fillet with a lemon slice.
Return to the oven and roast for 12-15 minutes, until the salmon is cooked through and the potatoes are fully tender.