If I have a cement roof that was poured years ago (4'X 4'X3") and I want to pour another roof over it (5'X10'X4") would the weight of the newly poured roof bear on the old poured roof once its set?  Or, would the new cornors take the majority of the weight?  Both roofs have wire mesh in them.  The small roof was once poured with the idea of being a cover over an entry but now I'ld like to make it a roof over a well house.  

This question is way to vague to answer because no one knows what is holding up the first slab, and what the capacity is of that bearing system.

Does one bear on the other...probably....BUT....no one knows if the walls below can handle the additional weight???

You need to have someone do a site review for you!