Older free versions (from circa 2015) are often incompatible with modern versions of SketchUp (2021–2025) due to changes in the Ruby scripting language. SketchUp Community Key Features of the NUI Version

The safest legal route for a free version is the SketchUcation forums. You do not need a subscription to download from there, but you will need a free forum account.

Unlike basic tools, it can model full rafters, beams, and eaves with decorative profiles.

If you are considering the official version, it offers significantly more automation than the older free scripts: Instant Roof Nui | Vali Architects | Instant Scripts