Preheat oven to 400°F (200°C).
Toss halved potatoes with olive oil, kosher salt, and rosemary on a large rimmed baking sheet.
Roast potatoes in the oven for 15 minutes.
In a small saucepan, whisk together maple syrup, soy sauce, Dijon mustard, and minced garlic.
Simmer the glaze over medium heat for 5-7 minutes until slightly thickened and syrupy.
Remove the baking sheet from the oven and push potatoes to one side. Place salmon fillets on the other side of the pan.
Season salmon with black pepper and brush generously with half of the prepared maple glaze.
Return the sheet to the oven and roast for 10 to 12 minutes until the salmon flakes easily with a fork and potatoes are tender.
Brush the remaining glaze over the salmon 2 minutes before the end of cooking to create a thick lacquer.
Serve the salmon immediately alongside the roasted potatoes.