After the design of your conservatory has been agreed, an important consideration is what the roof will consist of. For low pitch lean to roofs, 35mm polycarbonate is the usual choice, and comes in a variety of colours and variants, including heatguard. This reflects the sun in the summer whilst retaining more heat in the cooler times.
For most other designs, such as Victorian, Gable ended and Edwardian, there is more choice. You can use polycarbonate, or for superior sound proofing, 28mm toughened glass units can be used. Again, as with the polycarbonate roofs, the glass roof could be clear, grey or bronze antisun, to cut down the summer heat, or blue active to cut out the glare of the sun.