Road bike?

Need some help buying a road bike. What should I look for, its my first road bike. I competed in Ragbria http://www.ragbrai.org/ the last year on a friends bike and now need my own. What kind/speed, how big. I'm 230lbs and 6'3 Male
Update: edit... I did compete in Ragbrai Just it was against myself, and choosing not to sag any of the days. It was an easy ride, but my friends and I did race to certain stops, last one there bought for the others. Lets just say I nearly went broke. I did it on a mountain bike with road tires, so it can only get... show more edit... I did compete in Ragbrai Just it was against myself, and choosing not to sag any of the days. It was an easy ride, but my friends and I did race to certain stops, last one there bought for the others. Lets just say I nearly went broke. I did it on a mountain bike with road tires, so it can only get easier this time. And I also live in iowa
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