Line a baking sheet with parchment paper or a silicone baking mat. Preheat oven to 425°F.
In a medium-size bowl, mix together the potatoes, two tablespoons of oil, 1 teaspoon salt, and ½ teaspoon black pepper. Spread onto prepared baking sheet, and roast in preheated oven for 20-25 minutes, or until the potatoes have begun to soften, but aren’t completely tender.
While the potatoes cook, mix together the mustard, maple syrup, and dill in a small bowl. Set aside.
When the potato cooking time is up, push them to one side of the sheet plan, and then place the salmon fillets in the middle and the asparagus on the side.
Liberally spread the mustard mixture on top of the salmon. Then drizzle the remaining oil, salt, and pepper over the asparagus.
Roast in the preheated oven for 12-14 minutes, or until the salmon is opaque and flaky and the asparagus is fork tender, but not mushy. Serve with lemon wedges to spritz on the asparagus and salmon.