We are building a new home in south Florida. Open cell foam insulation of R-30 was recommended to us. We hired a contractor who sprayed 8" of open cell foam under the concrete roof deck. One week after the foam installation we had a heavy rain and our roof leaked and some of the foam got wet. We fixed the leak. two months has passed by and the foam is still wet and we know the roof is good, what is the problem with this product.

It could be taking a long time (or forever) to dry because of the high vapor-permeability and high capillary draw of the concrete continuing to transfer significant amounts of water inward. It doesn't take an out & out leak for this to happen. Open cell foam is fairly permeable at 8", thickness, but it's probably only drying toward the interior. If you have any vapor-retardent materials between the foam and the air-conditioned interior, it'll be slower still.

Can you describe a little better what the exterior roofing materials are, the pitch of the roof, and what's between the foam & fully-condtioned space?