Grind together ginger, garlic and two of the green chillies into a paste. Marinate chicken cubes in ginger-garlic-green chilli paste and salt for an hour.
Heat oil in a pan and sauté chicken cubes till done. Add cumin powder, chaat masala and check seasoning. Mix sliced onions and carrot strips.
To make kathi rolls, put one teaspoon of oil on a tawa and lightly heat the rotis. Smear each roti with one tablespoon of green chutney, place six to eight pieces of cooked chicken and sprinkle with remaining green chillies and coriander leaves. Spread a spoonful of onion and carrot mixture on the roti and sprinkle salt.
Roll the roti tightly over the stuffing and serve.