Preheat the oven to 400°F (200°C).
Line a large baking sheet with parchment paper or lightly grease it.
In a small bowl, combine the melted butter, lemon juice, lemon zest, minced garlic, chopped parsley, chopped dill, thyme leaves, salt, and black pepper. Stir well to create the lemon herb butter sauce.
Place the trimmed asparagus on one side of the prepared baking sheet in a single layer.
Place the salmon fillets skin-side down on the other side of the baking sheet.
Brush half of the lemon herb butter sauce evenly over the salmon fillets.
Drizzle the remaining lemon herb butter sauce over the asparagus and toss lightly to coat.
Roast in the preheated oven for 12 to 15 minutes, or until the salmon is cooked through and flakes easily with a fork, and the asparagus is tender-crisp.
Remove from the oven and let rest for 2 minutes before serving.
Serve the salmon fillets with the roasted asparagus alongside, spooning any remaining lemon herb butter from the pan over the top.