Is translucent fiberglass roof cooler or hotter than opaque roof
Technically speaking, the coolest thing to do is to have an opaque roofing surface that's a perfect mirror.  Short of that, it should be painted somewhere in the red spectrum, reflecting the infra-red range.
Beyond that, lighter colors are better.

Personally, I'd avoid the translucent, since I don't know whether long-term exposure to UV rays will damage the OSB.