Preheat the oven to 400°F and line a 9x13” baking sheet with parchment paper.
Add the potatoes to the sheet pan and toss with 2 tbsp oil, ½ tsp salt, ¼ tsp pepper, ½ tsp paprika, ½ tsp garlic powder, and ½ tsp onion powder. Roast for 20 minutes, or until the potatoes begin to soften and lightly brown.
While the potatoes cook, season the salmon with ¼ tsp salt, ¼ tsp pepper, and the remaining paprika, garlic powder, and onion powder. Set aside. 4. In a small bowl, whisk together the maple syrup, Dijon mustard, lemon juice, optional red pepper flakes, and ¼ tsp salt to make the glaze.
Remove the potatoes from the oven and push them to one-third of the pan. Add the green beans and tomatoes to the center third, drizzle with the remaining 1 tbsp oil, and season with the remaining salt and pepper. Toss to coat.
Place the salmon fillets on the final third of the pan and brush generously with the maple glaze, reserving some for later.
Return the sheet pan to the oven and bake for 12–15 minutes, or until the salmon flakes easily with a fork.
Brush the salmon with the remaining glaze, then broil for 1–2 minutes, watching closely to prevent burning.
Garnish with fresh parsley and serve warm.