(update: see a Mark Thoma rebuttal of Rogoff's argument. Thoma disagrees with the conventional wisdom of the "demographic timebomb" problem).
Rogoff's concern is that health care reform won't succeed in lowering the cost of health care, and will therefore break the bank. In other words: If we don't get health care reform right and soon, we're completely hosed:
Make no mistake, the US and much of the developed world is in a frighteningly precarious fiscal state. Exploding debt levels have remained manageable in no small part thanks to the extraordinarily low level of global real interest rates. Should the general level of global interest rates rise substantially, perhaps owing to a pick-up in emerging market growth over the next few years, a number of developed countries, including the US, may have to tighten their belts sharply in order to maintain stable debt ratios. Countries that fail to do so will suffer severe consequences, including spiralling interest rates and, ultimately, default by direct means or through high inflation.
It is a disgrace that the world’s richest country cannot provide reliable basic care for its poorest citizens. But if the politics of reform produces too extravagant a plan when the nation’s fiscal health is already so weak, the US may experience a form of financial crisis even more virulent than the one it is recovering from. Any healthcare plan would then be dead on arrival.