Here is a (very) short but cool primer on big bang:
This is an excellent example of the way scientists talk about origins. There is a definite acknowledgment of what we don't know (i.e. "before" the big bang) but then a listing of possibilities. Note that these are possibilities - not certainties. But then scientists are happy to live with unknowns - as that is where hot scientific questions thrive. Ideas of an oscillatory universe, multiverses or Brane-cosmology may all turn out to wrong or one of these may turn out to be correct. However, the verdict on these will only come from testing predictions - not from any theology or a particular religion. The only possible role for God in nature (if any) would have to be a theoretical "first cause" located at the end of an infinite regression of causes: we cannot ascribe "first cause" to big bang - as there may be a natural explanation behind it (and there already are several candidates). But we cannot ascribe a "first cause" to what is behind big bang, as there may be natural explanations behind those, and we me may uncover those sometime in the future. History of science tells us that even when we label a problem "unknowable" - it gets resolved with time. Origin of the Earth was once considered such a problem - so was the origin of the solar system. Both origins are very well understood today. I wouldn't bet against us figuring out the conditions that existed "before" the big bang.
Also see this earlier post Multiverse theory: Leave it to science.