In a skillet over medium heat, brown the sausage in 1-2 Tbsp. oil, breaking into small pieces until crumbly, and cook through. Remove sausage from pan and set aside.
In same skillet, stir fry chopped onion, bean sprouts, carrots and cabbage together in another 1-2 Tbsp oil, until vegetables are tender-crisp (about 5 minutes). Stir in cooked sausage. Season to taste with salt and pepper.
In a small bowl, make a paste using about 2 Tbsp. of flour with about 1 tsp. of water, and set aside. Lay an egg roll wrapper on your counter at an angle so that’s in “diamond” position. About ½ inch from the bottom corner, place 2 tablespoons of the filling. Take the bottom corner of the egg roll wrapper and lift it up and over the mixture. Next, take the right corner and fold it into the center. Do the same with the left corner. Roll it up tightly and then seal the tip of the top triangle with some of the flour and water paste. Repeat with the remaining filling and egg roll wrappers.
In a deep skillet, heat 1 inch of oil (or enough so that at least half of the egg roll will be submerged) to 375°. Fry the egg rolls, 3-4 at a time, for 2-3 minutes on each side or until golden brown. Drain on paper towels. Serve with sweet-and-sour chili sauce.