I'd go with a Shimano cassette hub, 36x3 double butted spokes, and a rim that weighs at least 450g. If you build with a >500g rim you should be able to make the wheel darn near bombproof.

I'd also recommend learning how to build it yourself. It's fun, rewarding, and you can achieve much better results than a machine or some guy that has no clue what he's doing if you're able to follow instructions carefully.

Then run the widest rear tire you can fit in your road frame. I'd recommend 32-35mm but 28mm is likely the biggest you'll be able to go if it's a "road racing" type bike.