Prepare the salmon fillets by seasoning with olive oil, lemon juice, mustard, grated garlic, parsley, black pepper, paprika, red pepper flakes, and salt
Prepare the roasted vegetables by cutting potatoes, carrots, red onions, and mushrooms into appropriate sizes
Toss vegetables with olive oil, dried thyme, paprika, garlic powder, black pepper, and salt
Bake salmon and vegetables in the oven until salmon is flaky and vegetables are tender
Prepare the lemon dill mustard sauce by melting butter and whisking in flour to create a roux
Gradually add milk to the roux, stirring constantly to avoid lumps
Add fresh dill, mustard, lemon juice, and grated garlic to the sauce
Season the sauce with salt and black pepper to taste
Serve the oven-baked salmon with roasted vegetables and drizzle with lemon dill mustard sauce
