I'm not sure if I'm stating the obvious here, but from the context and the way you ask it there could be a misunderstanding about the term "rootfs".

It means "root file system" - if you're used to Windows, from a user perspective it's a bit like drive C: (OK, everyone else, I know this is plain wrong from a technical point of view, but it gets the point across, doesn't it ...)

So it's not something you want to delete (you don't delete C: ...), it's something you want to delete things from to make space available again.

To make space available, uninstall applications you got from extras-devel and extras-testing. Many of those are in early stages of development and use much more space on the root file system than they should.