Pour warm water into a heatproof bowl until half full. Dip 1 rice paper wrapper in water. Place on a flat surface. Stand for 20 to 30 seconds or until soft enough to roll without splitting.
Place one-eighth of lettuce along 1 edge of 1 wrapper. Top with one-eighth each of beansprouts, carrot, cucumber and avocado. Fold in ends. Roll up firmly to enclose filling. Cover with a damp tea towel to prevent roll drying out. Repeat with remaining wrappers, lettuce, beansprouts, carrot, cucumber and avocado. Serve with sweet chilli sauce.