Prep the filling: Chop lettuce, julienne carrots and cucumber, thinly slice bell pepper, pick cilantro and mint leaves, and slice the avocado.
Set up your station: Fill a shallow dish with warm water. Set a clean surface (or large plate) beside it, and keep a damp towel handy to cover finished rolls.
Soften the wrapper: Dip 1 rice paper wrapper into the warm water for 10–15 seconds until just pliable (it will keep softening as it sits).
Add the fillings: Lay the wrapper flat. Near the bottom third, add a small handful of lettuce, a few carrot and cucumber sticks, a few pepper strips, 1–2 avocado slices, and a pinch of cilantro and mint. Don’t overfill.
Roll it up: Fold the left and right sides inward over the filling. Roll up from the bottom, keeping it snug, until sealed.
Repeat: Continue with remaining wrappers and filling. Keep rolls covered with the damp towel so they don’t dry out.
Make the dip: Whisk soy sauce, lime juice, and sesame oil in a small bowl.
Serve: Arrange rolls on a platter and serve with the dipping sauce.