Take the chicken mince in a bowl. Add onion, green chillies, salt, ginger paste, chaat masala, garam masala powder and mix. Take some water in another bowl and dampen your hands. Take a portion of the chicken portion, roll in a ball and wrap it around a skewer. Gently press to make seekhs. Heat oil on a tawa, put the seekhs on and cook. Add more oil and turn to cook on all sides. Heat the prepared rotis (roomalis or normal) on a tawa. Take yogurt in a bowl. Add green chutney and mix. Apply this on the rotis, put sliced onions over it, place a chicken seekh, sprinkle some chaat masala, fresh mint leaves and roll. Serve hot wrapped in a foil or paper napkin.