For the dressing, mix the ingredients until emulsified. I like to shake them in a jar.
Pour water into a shallow dish and dip the rice paper for 2-3 seconds per side. Transfer to a damp cutting board. Trust me, it sounds easier than it looks. Add 1 layer of smoked salmon, then cucumber slices, spinach, onion, avocado, capers, herbs, and romaine. They don't all need to be the same. Gently roll like a burrito. Cover with a damp towel to keep fresh.