Blueberry Filling:

1. In a medium saucepan over medium heat, combine the blueberries, sugar, and lemon juice with 3 tablespoons of water. Allow the mixture to cook until the blueberries start to burst.
2. Dissolve the cornstarch in the remaining tablespoon of water and stir it into the blueberry mixture. Continue cooking until the mixture thickens. Remove from heat and let it cool.

Cream Cheese Filling:

1. In a bowl, beat the cream cheese with sugar, lemon juice, and vanilla until the mixture is fluffy and smooth.

Assemble and Fry:

1. Lay out an egg roll wrapper on a clean surface. Spoon some cream cheese filling onto the wrapper, and top with a spoonful of blueberry filling.
2. Wet the edges of the wrapper lightly with water, fold in the sides, and roll tightly to ensure the fillings are sealed in.
3. Heat the oil in a deep fryer or large skillet to 350°F (175°C). Fry the egg rolls until they are golden brown and crispy, about 2-3 minutes on each side.
4. Drain on paper towels and dust with powdered sugar before serving.