Also new to road biking and had some similar problems. I found that the real solution is to get the weight off your hands and wrists by varying hand position and more importantly, improving your core strength to support your upper body rather than using your arms to support your weight. I also thought that it was fit related, but when I had a professional fitting, very little was changed in my position. But the fitter did give me some tips on riding that helped a lot. On my last 1.5 hour ride I had no problems with numbness. Gripping the tops of the bars rather than riding the hoods specifically helped a lot in my case.