I made a RetroPie 3.2.1 image for NOOBS using this guide.
Once you downloaded the file, verify archive integrity, extract the folder ‘RetroPie’ and place it in ‘os’ folder in NOOBS installer.
Copy NOOBS files to MicroSD and start installation process.
MD5: bd740448161dc088adda87e15c623cfb
https://drive.google.com/file/d/0B6BapBqVYAx2UEkxNm9pOVdKUEk/view?usp=sharing
N.B: I did not change the installation slides of Raspbian.
Dai retta a un cretino 