Bring a large pot of water to a boil. Remove from the heat and add rice noodles. Let soak for 8 to 10 minutes, until noodles are soft but firm, stirring occasionally. Drain well.
Fill a bowl with hot water (not boiling). Submerge 1 sheet of rice paper into the water until soft, about 15 seconds. Place rice paper on a work surface and lay 1 piece of lettuce in the middle, starting at the bottom. Add some rice noodles, cabbage, sprouts, cilantro, carrot, avocado, and bell peppers. Pull up the bottom of the rice paper and roll up and over the vegetables. Fold in the sides of the sheet to seal. Repeat to make remaining rolls.