Heat oven to 425°F and line a rimmed sheet pan with parchment.
Whisk the Dijon, maple syrup, lemon juice, garlic, 1/4 tsp salt and pepper in a small bowl.
Toss broccoli with olive oil and the remaining 1/4 tsp salt, spread in an even layer and roast 8 minutes.
Pat salmon dry, nestle among the broccoli, and spoon half the glaze over the fillets; keep the rest untouched for serving.
Roast 12-14 minutes, until the salmon reaches 145°F and flakes easily.
Drizzle the reserved glaze over the salmon and serve.