In a large bowl, combine the cooked rice, sesame oil, and salt. Mix well until the rice is evenly coated and slightly sticky.

Place a sheet of nori on a bamboo sushi mat or a clean surface, shiny side down. With wet hands, spread about 1/2 cup of the rice mixture evenly over the nori, leaving a 1-inch border at the top.

Arrange a line of beef, spinach, carrot, and pickled radish across the center of the rice.

Starting from the bottom, carefully roll the nori away from you, using the mat to help keep the roll tight. Press gently to seal the edge of the nori.

Repeat the process with the remaining sheets of nori and filling ingredients.

Once all rolls are made, use a sharp knife to slice each roll into bite-sized pieces. Wipe the knife with a damp cloth between cuts for cleaner slices.

Sprinkle sesame seeds on top if desired and serve with soy sauce for dipping.