Combine rice wine vinegar, 1 tablespoon sugar, and salt. Add the julienned carrot and radish and marinate for 30 minutes. Drain well.
Combine mayonnaise, sriracha, and hoisin. Mix well. Feel free to add more sriracha if you prefer a spicier sandwich.
Mix fish sauce and remaining 1 tablespoon sugar. Pour this over the pork and toss well.
Preheat an oven to 400 degrees F.
Split the rolls from the top, being sure not to cut them completely in half. Toast in the oven for 2 minutes, or until just crispy.
To assemble, spread some of the mayonnaise on one side of each bun. Spread the pâté on the other side. Divide the roast pork among the 12 buns. Top with cucumber slices, pickled vegetables, and cilantro.