Slice beef thinly. Put into a bowl with rice cooking wine, 2 teaspoons sugar, soy sauce and oyster sauce. Rub the beef with sauce to coat well. Set aside.
In a bowl, mix together julienne carrots and 1/4 teaspoon salt. Let sit for about 10 minutes until carrots are tender.
In a fry pan or skillet, heat olive oil, put the beef with the sauce and cook beef over medium heat until cooked through. Remove from the heat and set aside.
After 10 minutes when the carrots are tender, make namuru. Squeeze the carrots to drain completely. Put into another medium-large bowl and add julienne cut cucumber, sesame oil, 1/2 teaspoon sugar and 1/4 teaspoon salt. Mix to combine. Set aside.
Make gochujang butter. In a small bowl, mix together gochujang and butter. Spread the gochujang butter on the bottom, cut side, of each roll and place on a baking sheet with the top of rolls. Bake at 375 degrees F oven for about 5 minutes.
Build sandwiches. Take the rolls out of the oven. Put green lettuce leaves on the bottom of roll (on the gochujang butter). Put the beef (drip off the sauce) on the lettuce. With hands, squeeze namuru to drain and put on the beef. Put the top of roll to close sandwich. Make one more sandwich.