I got an eRoll awhile back and I like it a lot.  For me, it's perfect for when I'm working since I can hold the thing in my mouth and have both hands free for typing (like a real cigarette only no ashing ), but the charging case can be a pain.  To fit in the PCC, the eRoll has to be fully assembled; battery, atomizer, cone, and tank.  The eRoll kit comes with 2 of everything, except a second cone. 
  
Anyways, the 5100CC battery seems to be the same as an eRoll's, so I should be able to use that right?  I'm curious how the battery stays in the charger though since there's no threading, possibly magnets maybe (how do magnets even work?) 
http://www.joyetech.com/product/510CC.php