This story never finishes.
For history, the culprit is poly2_b{2} command, which was broken in 16.
The failure of the roof accessory in 2D was a consequence of this bug.
The bug was noticed in July 2012, and fixed with hotfix 4 (3827), one year later.
In AC 16 (3827), poly2_b{2} command is repaired
Opening Roof Surfacer 16 (3827), you will see at line 46 (2D Script).
beta=0
In AC 17, poly2_b{2} command is repaired… and Roof Surfacer 17 is broken again.
The previous line of code is missing.
As a temporary workaround, add this line at the begining of the 2D Script
beta=0
Do a copy not to modify the original library. Wait for the next Library Hotfix.
Keep cool.