Blueberry Cream Cheese Egg Rolls

1 cup blueberries, fresh or frozen
1/4 cup sugar
1 tablespoon lemon juice
1/2 teaspoon cornstarch
8 ounces cream cheese, softened
1/4 cup powdered sugar
1 teaspoon vanilla extract
12 egg roll wrappers
Vegetable oil, for frying
Powdered sugar, for dusting (optional)