legobazooka

I assume by isolation you are refering to what in the UK is known as insulation? In which case I hope you left an airgap between the insulation and the roofing material. This airgap is essential for proper ventialtion to prevent condensation which can then lead to rot setting in the rafters. The recommended gap is 50mm (2 inches). Hope this helps, would hate to hear you had problems in the future.