Mix tomato paste, half the lime juice and all the ground coriander in a shallow dish. Add the steak, turning to coat. Refrigerate for 30 minutes.
Whisk the remaining lime juice, the sugar, salt and chilli flakes in a large bowl. Add the cabbage, carrot, capsicum, coriander and mint; toss thoroughly to combine. Refrigerate coleslaw until serving time.
Preheat grill. Remove steak from marinade. Cook 15 cm from heat for 4 minutes per side for medium-rare, brushing any remaining marinade over steak halfway through the cooking time. Let stand for 10 minutes. Cut steak diagonally across the grain into thin slices. (Steak can be cooked on a barbecue.)
To serve, fill rolls with coleslaw and top with steak.