Cook the rice noodles according to package directions. Drain well and rinse until cold. Trim the green onions and cut into 2-inch lengths. Stack green onions and slice lengthwise to create very thin strips.
While noodles cook, in a medium bowl, combine the hoisin sauce, peanut butter and vinegar. Whisk in 2 tablespoons warm water until smooth. Add the peanuts, if using. Set aside.
Fill a wide shallow dish or pie plate with very warm water. Working with 1 rice paper wrapper at a time, place in water and soak for 15 seconds, until soft. Transfer to cutting board and spread out flat.
In center of 1 wrapper, arrange 2 lettuce pieces. Top with about 1/4 cup noodles. Arrange some bell pepper, green onions and herbs on top of noodles. Fold sides of wrapper over filling. Fold bottom of wrapper up over filling, tucking under to create tight roll. Roll up to seal. Place on plate under damp paper towels. Continue filling and rolling with remaining ingredients. Serve with dipping sauce.
Tip: Add cooked shrimp, chicken or pork to rolls or swap out bell pepper for carrots in these versatile rolls. Replace romaine with baby spinach or other greens.