[extesy]

This article has a section titled "how Roaring bitmaps are represented in memory". I suggest you actually read the article, it will likely answer all your questions.

[Xeoncross]

I was actually asking how they were serialized and stored on disk.

[jpgvm]

The on-disk format is documented in the spec: https://github.com/RoaringBitmap/RoaringFormatSpec

It's very simple actually. I worked on adding run container support which involved adding support for the newer serialization format in roaring-rs and it proved quite elegant.