The tandoor is a cylindrical clay oven heated to 400–500°C. Roti dough is slapped onto the inside walls, puffing and charring in under 2 minutes. At home, we get surprisingly close by inverting a heavy baking tray, preheating it under the grill (broiler) for 15 minutes until it's as hot as possible, and pressing rolled roti directly onto it. The key is maximum heat from above the grill and below from the scorching tray. You'll get char spots, puffing, and that characteristic soft-chewy interior.
The dough is simple — just whole wheat flour, water, salt, and a small amount of oil. The hydration level and rest time are what matter. Properly rested dough rolls thin without tearing and puffs dramatically in the oven.