Prepare the sauce by combining the hoisin sauce, peanut butter, sriracha and grated ginger. Add 1/4 cup of hot water and whisk the ingredients together. Continue to add hot water until the sauce is the consistency you desire. I used 1/4 cup plus two more tablespoons of hot water.
Gather and prepare the filling ingredients. Slice the red bell pepper and mango, soak the bean threads, chop the lettuce and pull the cilantro leaves from the stems.
When your fillings are ready to go, take one rice paper wrapper at a time and soak it in warm water for five seconds or until it is soft and limp like a wet paper towel. Lay the soft wrapper on a clean surface, place the fillings on top near one side and then roll the wrapper around them. Fold the left and right sides in as you roll to close up the ends. Here is an excellent video of how to roll them.