1. To make dipping sauce: Combine first 5 ingredients (through scallion) in a small bowl; refrigerate.
2. To make rolls: Fill a large shallow dish with warm water. Wet a clean kitchen towel; wring out and place on a clean work surface. Place 1 rice paper sheet in warm water; soak to soften (about 30 seconds). Remove from water; place on kitchen towel. Working quickly, place 2 basil leaves facedown in center of paper, leaving 3 inches at bottom of paper and about 1 1/2 inches on each side. Place 3 pieces lettuce on top of basil; mound 2 tablespoons noodles on top of lettuce. Top each with mango strips (1/4 ounce) and 4 shrimp halves. Arrange 2 mint leaves, face-side up, on top of shrimp. Pull bottom of wrapper over filling, fold in sides, and roll wrapper into a cylinder. Repeat with remaining ingredients; serve with dipping sauce.