I realize Rigify was not meant for games but I have used it without much problem through many versions of Blender.
I just now noticed however that the foot roll doesn’t animate in BGE. I imagine it has something to do with the fact that it uses a scripted driver but then the neck also seems to do so and works fine.
This shows that it is not just scripted drivers. Compare the animation you get in 3D view (the box rotates driven by the ball dropping) with what you get in the game engine (the box is totally still).