The roof is a part of your house where a lot of heat can be lost.
If you have rooms in the roof, installing insulation is not straightforward, though there are options available, but if you have a loft space, this is an area which is easy to improve.
Most houses have some insulation in their loft, commonly about 10cm. Current Building Regulations require a minimum of 27cm. The additional insulation can easily be applied over the top of what you already have, either as mineral wool (the light fluffy stuff), or if it is boarded or the ceiling joist tops are still visible, with a rigid insulation board.
Mineral wool needs to be thicker than the board, but is cheaper. The insulation board, while dearer, has the advantage that you could still use your loft space for storage.
Whether you have a loft space or a room in the roof, we can give you further guidance to suit your particular situation. If you have any queries, please email firstname.lastname@example.org.