That is most definitely an ABS roof. You don't need to rebuild it. Since it has started de-laminating, you just need to remove all the ABS. Under that you will have a perfectly good roof. You will need to use Grizzly Grip to completely cover the rood under the ABS. There are a a few extra steps involved, but nothing complicated. Just like sanding and wiping down with acetone. The Grizzly Grip will provide you are a perfectly sealed roof for a lifetime. Just try to peel all the ABS away. There is no wood in that roof to rot or replace. It's much easier to deal with than most roof issues.