In a medium bowl, combine corn, onion, tomato, cilantro, lime juice, vegetable oil, and salsa rocoto. Season with salt and pepper to taste.
In a large pot with a tight-fitting lid over high heat, bring white wine to a boil. Add mussels, then cover and cook until mussels are open, about 3 minutes. Drain. Discard any closed mussels.
Shuck mussels, leaving them on the half-shell. Top each mussel with a spoonful of corn salsa. Arrange on a serving platter or individual plates (6 or 7 mussels per person). Garnish with lime wedges and cilantro leaves.
Peruvian Pantry: Salsa Rocoto. Aji rocoto is a chile somewhat like a red jalapeño. Salsa rocoto is a puréed sauce made with this chile and is available at many Latin markets. Asian Sriracha hot sauce makes an excellent substitute.
Note: Nutritional analysis is per 6-mussel serving.