Preheat the oven to 425°F (220°C). Line a large sheet pan with parchment paper or aluminum foil.
In a large bowl, combine the halved baby potatoes, olive oil, garlic powder, onion powder, dried oregano, grated Parmesan cheese, salt, and black pepper. Toss well to coat evenly.
Spread the seasoned potatoes in a single layer on one side of the prepared sheet pan.
Roast the potatoes in the preheated oven for 15 minutes.
While the potatoes begin roasting, prepare the honey mustard sauce by whisking together Dijon mustard, honey, mayonnaise, lemon juice, smoked paprika, and salt in a small bowl.
After the potatoes have roasted for 15 minutes, remove the sheet pan from the oven. Push the potatoes to one side to make space for the salmon fillets.
Place the salmon fillets skin-side down on the empty side of the sheet pan.
Brush each salmon fillet generously with the honey mustard sauce.
Return the sheet pan to the oven and roast for an additional 10 minutes, or until the salmon is cooked through and flakes easily with a fork, and the potatoes are tender and golden brown.
Remove from the oven and garnish with chopped fresh parsley before serving.