Here is a Triple-Boot build of RetroPie 3.6, OpenELEC 6.0.3 (Isengard) and Raspbian Jessie:
USB install is highly recommended for this build due to the size of the install files!
As usual, full install steps / troubleshooting etc. can be found in the readme file.
Sill using an unofficial build of NOOBS USB installer so like my other builds – use at your own risk! (I have had no complaints so far and it works great for me).
All the best, Steve