Preheat the oven to 425°F (220°C). Line the sheet pan with parchment paper if desired for easy cleanup.
In a mixing bowl, combine the broccoli, carrots, bell pepper, and red onion. Drizzle with 2 tablespoons of olive oil and season with salt, pepper, and garlic powder. Toss to coat the vegetables evenly.
Spread the vegetables in a single layer on one side of the sheet pan.
In the same mixing bowl, place the salmon fillets. Drizzle with 1 tablespoon of olive oil, lemon juice, paprika, salt, and pepper. Rub the seasoning into the salmon.
Place the salmon fillets skin-side down on the other side of the sheet pan, beside the vegetables.
Roast in the preheated oven for 15-20 minutes, or until the salmon is cooked through and flakes easily with a fork, and the vegetables are tender.
Remove the sheet pan from the oven and let it cool for a couple of minutes. Garnish the salmon with fresh parsley before serving.