A Rozière Balloon is a special balloon-airship hybrid found on several locations on the map: Istanbul to Beirut, Baghdad to Tehran, and Port-au-Prince to Washington. There is also a similar airship from Brisbane to Auckland, but it is not considered a Roziére Balloon, instead just a plain Hot-Air Balloon - however, you can use it on the trip if you either have the cursed dagger or traveled on the airship between Colombo and Chittagong, and this will allow the balloon to safely arrive in Auckland after flying over a storm.
The Roziére Balloon from Istanbul is only accessible after Passepartout meets a young medical student hoping the flee to political instability of the city. Bewitched by Passepartout (who is still wearing Harem Silks from a misadventure the night before) he does not charge for the journey.
However, if Passepartout has acquired a real Preparation of Paraffin from the Artificer of Bucharest, any of the three Roziére Balloon routes may be sped up so that the journey will take only a single day.