Don’t think it is possible to fit a normal cluster to a Rohloff. If you could you would have to increase the rear dropout spacing. Saying all of that I have got a feeling that Sheldon Brown has done it (couldn't find it on his site.)
Don't know why you would want to do it, as you would end up with a VERY complicated gearshift, less reliability and dreadful gear overlap. The 14 equally spaced gear ratios on the Rohloff are more than enough for most of us!
