Preheat oven to 400°F.
In a bowl, combine the 2 medium peeled and diced sweet potatoes (1-inch cubes) with 1 tablespoon olive oil, 1 teaspoon dried rosemary, 1/2 teaspoon onion powder, 1/2 teaspoon garlic powder, and salt and black pepper to taste. Toss until evenly coated.
Spread the seasoned sweet potatoes in a single layer on a baking sheet.
Bake the potatoes for 15 minutes, until they begin to soften.
While the potatoes bake, drizzle the 2 salmon fillets (6 ounces each) with the remaining 1 tablespoon olive oil and season with salt and black pepper to taste.
Remove the baking sheet from the oven, push the sweet potatoes to one side, and place the salmon fillets on the other side of the sheet with space around them.
Return the baking sheet to the oven and bake 10–15 minutes more, or until the salmon is cooked through and flakes easily with a fork.
Remove from oven and serve.