How to Make It
Heat oven to 450° F. Season the pork with the cayenne and ¼ teaspoon salt. Roast on a rimmed baking sheet until an instant-read thermometer inserted in the center reaches 145° F, 20 to 25 minutes; thinly slice.
Meanwhile, combine the cucumber, vinegar, oil, brown sugar, and ¼ teaspoon each salt and black pepper in a medium bowl.
Divide the mayonnaise, pork, and cucumber among the rolls.