I think you mean Enviromat - a living carpet of Sedum plants grown on matting. It would grow on a shed roof with a slope up to 30 degs, but there are some points to consider.
Firstly, you must check the roof is in good condition and is waterproof. Bear in mind that once the Enviromat has been installed and is growing, it will be difficult to repair any leaks in the roof. You also need a root barrier to ensure the roots will not damage the waterproofing. Then a water retention mat needs laying and you must ensure it is in contact with the surface - and then the Enviromat is laid on top.
Standard rolls of Enviromat are 1m wide. You need to consider how the Enviromat will be handled since a 2m roll can weigh up to 80kg.
More information can be obtained from Q Lawns on 01842 828266. Your nearest suppliers are likely to be Richard Abel Landscapes of Sundridge, Kent, or Sempervirens at Bridge Farm Nursery, Whitton, near Twickenham.