Floating images via [role=left] does not work in the github rendered version of asciidoc. See for example:
https://github.com/kovidgoyal/kitty/blob/c8fc0394e3cca8f659d8833aab8bb25762865be9/README.asciidoc
That document when redered using asciidoctor has a floating image, as expected, but not when rendered by github.