In small bowl, combine peanut butter, rice wine vinegar, sesame oil, and tamari. Add water, a little at a time, and mix slowly with a fork or spoon to gradually loosen the stiff peanut butter mixture. Once sauce is smooth, if you want a looser consistency, add more water, a teaspoon at a time. Once you’re happy with the consistency, add gingerroot, garlic, and red pepper flakes; mix through, and then pack into a sealable container.
To assemble rolls, first set out a clean cutting board for your workspace. Fill a wide, shallow bowl with hot (not boiling) water and, working quickly, soften one wrapper in water and lay it on your cutting board. Place 3 mint leaves and 3 radish slices on wrapper. Add lettuce, fill with cashews, a few slices of broccoli, and a few carrot matchsticks, and finally spinach. Roll tightly and repeat with remaining wrappers until you have 8 rolls.