Preheat the oven to 425 degrees . In a large, ovenproof skillet, heat 1 1/2 tablespoons olive oil over medium-high heat. Add the potatoes and mushrooms, season with salt and pepper and cook, stirring occasionally, until lightly browned, about 5 minutes. Transfer to the oven and roast for 10 minutes. Stir in the asparagus and roast in the oven until the asparagus is crisp-tender, 2 to 3 minutes.
Meanwhile, rub the salmon all over with 1 tablespoon olive oil and season with salt and pepper. Arrange the salmon, skin side down, on a foil-lined baking sheet; roast until opaque in the center, about 10 minutes.
In a small bowl, whisk together the parsley, garlic, lemon peel, lemon juice and remaining 1 1/2 teaspoons olive oil; season with salt and pepper. Toss with the roasted vegetables and serve with the salmon.