A roof module is a complete top for a convertible.
The OEMs finally are completing their cars in their own production lines with these tops to a convertible.
Depending on the OEM it is possible that these suppliers are working as a full service vehicle supplier and are producing the complete cars (e.g. Karmann, Heuliez or Pininfarina).
Car Top Systems, Edscha and OASys (Automotive) are not full service vehicle suppliers and are delivering just the top to the OEMs.
This article about an automotive part or component is a stub.