Prepare the Blueberry Filling: In a medium saucepan, combine blueberries, sugar, cornstarch, lemon juice, and cinnamon.
Cook the Filling: Place saucepan over medium heat, add water, and stir. Cook until blueberries soften and mixture thickens, about 5-7 minutes. Cool completely.
Prepare Egg Roll Wrappers: Unroll pie crusts and cut each into 6 squares.
Fill the Egg Rolls: Place a pie crust square flat and spoon about 2 tablespoons of cooled blueberry filling in the center.
Fold the Egg Rolls: Fold one corner over filling to form a triangle, seal edges. Fold side corners towards center, overlapping. Roll up tightly.
Seal the Egg Rolls: Brush final edge with beaten egg and press to seal.
Fry the Blueberry Egg Rolls: Heat vegetable oil to 350°F (175°C). Fry egg rolls in batches for 2-3 minutes per side until golden brown and crispy.
Drain and Cool: Remove from oil and drain on paper towels. Cool slightly before serving.