No nation can roll their debt over indefinitely.
Yes, they can. The absolute level of public debt is not what matters. The debt/GDP ratio is what matters. If raising the public debt 1% raises GDP 5%, then it is in the countries best interest to raise the public debt 1%, and roll over that debt indefinitely.
One can't have an national debt rising infinitely.
As long as GDP is rising faster, yes one can.
One can say what one wants of Germany, but at least they got their budget in order, and they don't structurally spend more then they get, not is their national debt getting out of control. If every country followed that - or had followed that, like Greece - things would look a lot better.
Governments are not households. Macroeconomics is not microeconomics. It is more important for governments to minimize unemployment (with productive jobs, not breaking windows and then fixing them) than it is for them to pay down public debt.