1. Heat oven to 450°F. On rimmed baking sheet, toss potatoes with 2 tablespoons oil, then five-spice powder and 1/4 teaspoon salt. Transfer half to second baking sheet and arrange all in single layer. Roast until crisp, 20 to 25 minutes.
2. Meanwhile, in food processor, pulse salmon, soy sauce, and sesame oil 4 to 5 times, just until coarsely chopped. Add scallions and pulse to combine. Form mixture into four 3/4-inch-thick patties.
3. Heat remaining tablespoon oil in large nonstick skillet on medium and cook patties, turning once (do not flatten), until opaque throughout, 2 to 3 minutes per side. Transfer to buns and top with avocado and sprouts. Serve with sweet potato fries.
Nutritional Information (per serving): 675 calories, 37 g fat (5.5 g saturated), 37 g protein, 735 mg sodium, 50 g carbohydrate, and 9 g fiber.