How can I roll a cube (around its edges) with armatures? I want to set up an animation of a rolling cube for a video game. 
The cube needs to roll/tumble to all its sides. 

When I add bones to the cube, only the parent bone seems to make the whole cube rotate (obviously) but when I rotate the next 'child' bone, the parent bones stays put...

How can I connect all the bones with each other (like my skeleton is one stiff bunch of bones) in order to make the whole cube rotate when I rotate a child bone?
This is just what you need! This is a Wolfram Alpha widget that showe you the cylogons (roulletes on n-gons about a straight line). The square is a default option:

http://demonstrations.wolfram.com/TracingACyclogonRouletteOfAPolygonRollingAlongALine/

EDIT: I made a canned animation of this rolling motion here, maybe you can use it:

http://pasteall.org/blend/index.php?id=51926