When a roof space is converted into a room, it requires a different type of insulation that will fit into gaps between joists and behind walls of the room.
This type of insulation helps to improve the energy efficiency of a building by reducing heat loss through the roof.
Without this insulation, the room in the roof will be highly susceptible to temperature changes in both summer and winter; in addition, if there is no insulation the rest of the house will suffer from the heat loss in the winter, which can increase your energy bills.