We love RetroPie, and recently commented that I have several SD cards. Many times we miss, because you never will go to fill a 16 or 32 GB SD Card, so Berryboot comes to the rescue to install more than one distribution to a SD Card.
A user has been kind enough to share with us a pretty elaborate tutorial to copy RetroPie and any other operating system on a SD Card with Berryboot.
Thanks Mirror from all of us.
Download: pdf - Install RetroPie on BerryBoot