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.
The three things that I ask people to consider when they're replacing a roof is if they're in a wind or hail damage region, and if they're in a region with high solar gain (such as Texas) or an area prone to ice damming (such as New England or the upper midwest.)
If you're in an area that is prone to wind or hail damage (thunderstorms or hurricanes), you might want to look into a more resilient form of roofing material. Stone-coated steel shingles (which look just like standard asphalt shingles) are a great product that will resist most forms of damage that can be dished out. Your insurance may give you a discount on them because they have a longer lifetime.
If you're in a high solar gain area, look into some of the energy-star rated shingles. They again look just like stone coated asphalt shingles, but they'll help keep your attic cool in the summertime.
If you're in an area that gets a decent amount of snow, make sure that they install an ice & water barrier around any roof penetrations (like skylights or places where they replace a vent) and along the edge of the roof where you could develop ice damming problems. This material is a sticky membrane that self-sticks to the roof deck and basically keeps water from seeping through at all. Common brand name for this product are "Grace Ice & Water Shield" ... I also personally use it in roof valleys, gable crotches, and several other places where water tends to get blown up inside something and you really don't want it to soak through.
You definitely want to get your insulation up to the max, but that's something that you can do at any time using blown-in insulation. If you are replacing roof decking and have it open, you should make sure that you have plenty of soffit vents and that your soffit vents are baffled properly. (I like the Berger Accuvent, personally...)
You want to make sure that any damaged or rusted flashing is replaced, and that tar paper is replaced. Look into what kind of tar paper they're using (heavier the weight, the better...), because that's actually your roof. Make sure you know what kind of valleys you're getting. For standard asphalt shingles, I prefer woven valleys, but they're harder to do and therefore are more expensive.
Best Answer
The same policy goes for roof sheathing as for hanging drywall, you get more strength by spanning more rafters/joists/studs and offsetting the joints. This solves two points of weakness.
The main one is the structure turning into a parallelogram where the studs are no longer perpendicular to the ground. When you think of using a diagonal brace to support a wall, you want to get both ends as far apart as possible. If you install vertical, then that gives you the support of a diagonal brace spanning 4' worth of studs. But by staggering the joints and going horizontal, you get the equivalent 12' or more of studs braced.
The other form of support you get is for vertical load on a roof segment. If you stand between two rafters and the sheathing was laid vertically, you are closer to a seam where the nails could pull away under load and you can fall through. Holmes on Homes had an episode where they were replacing a leaking roof and the builder laid a patch where the owner decided not to go with the skylight option. The patch was laid vertically, and they almost fell right through the roof.