Preheat oven to 450 degrees F. Lightly coat a large baking sheet with nonstick cooking spray; set aside. For filling: In a medium nonstick skillet, heat oil over medium-high heat. Add pork, sweet pepper, ginger, and garlic. Cook for 3 to 4 minutes or until pork is no longer pink, stirring occasionally. If using ground pork, drain off fat. Add bok choy, water chestnuts, carrot, and green onions to pork mixture in skillet. Cook and stir about 1 minute more or until any liquid evaporates. Stir in vinaigrette. Cool filling slightly.

For each egg roll, place an egg roll wrapper on a flat surface with a corner pointing toward you. Spoon about 1/3 cup of the filling across and just below center of each egg roll wrapper. Fold bottom corner over filling, tucking it under on the other side. Fold side corners over filling, forming an envelope shape. Roll egg roll toward remaining corner. Moisten top corner with water; press firmly to seal.

Place egg rolls, seam sides down, on the prepared baking sheet. Coat the tops and sides of the egg rolls with nonstick cooking spray. Bake for 15 to 18 minutes or until egg rolls are golden brown and crisp. Cool slightly before serving.