Debian testing might work. I don't know if it is technically a rolling release distro but it stays up to date. Also OpenSuse tumbleweed. And there's a similar Fedora distro: rawhide, maybe?
I don't really know, I haven't seriously used unstable. That being said, I like testing because the packages are generally new enough for my purposes but they've also had more vetting, so I don't have to worry about a broken system as much.
