Heat oven to 425 degrees.
On a rimmed baking sheet, toss sweet potatoes with 1 tablespoon oil. Season with salt and pepper. Roast, tossing occasionally, until golden and tender, 20 to 23 minutes. During the last 10 minutes of cooking, brush fish with remaining oil and season with salt and pepper. Roast on a second baking sheet until cooked through, 8 to 10 minutes.
Squeeze fish and roasted sweet potatoes with lime and sprinkle with parsley.