In a small bowl, stir together the hand vinegar.
Lay a sushi mat on a clean surface and cover with plastic wrap. Moisten hands with hand vinegar and shake off excess. Lay 2 pieces of roast beef on the mat to cover it.
Sprinkle with some chili powder and ¼ of the garlic, rubbing both into the beef with your fingers. Cover the beef with 1 cup sushi rice, leaving 1 inch empty at the end farthest from you.
Zest the limes and sprinkle ¼ of the zest over the rice. Squeeze a little lime juice over the rice as well. Sprinkle the rice with cumin seeds.
Arrange one quarter of the jalapeño and scallion strips, two cilantro sprigs and a sprinkling of cheese along the center of the rice, crosswise, covering the half of the rice that is closest to you.
Securing the jalapeño, scallion and cilantro with your fingers, use your thumbs to push the end of the mat up and over the filling, until the one edge of the rice meets the other side. Press firmly on the roll to seal and shape.
Lift up the top of the mat and roll firmly until tight and round. Squeeze gently to shape the roll. Press the ends in carefully to secure any loose rice. Remove the bamboo mat, peel off the plastic and set the roll aside.
Repeat with the remaining ingredients to make four rolls. Slice each roll into six-eight rounds, arrange on a sushi platter and serve with pico de gallo or salsa.