Romney's op-ed from USA Today is reproduced here.
The relevant portion below is argued in opposition to strong efforts at the time, particularly in the US House under Nancy Pelosi, to pass a healthcare reform bill which included the public option, or government insurance.
Romney's idea, as with RomneyCare in Massachusetts, was to shun the public option in favor of mandated purchase of privately supplied health insurance, under penalty of a tax, which is what we got with the Senate version of healthcare reform now known to us as ObamaCare, under which the tax is called a fine in order for the president to be able to claim that he does not raise taxes on ordinary Americans:
"Our experience also demonstrates that getting every citizen insured doesn’t have to break the bank. First, we established incentives for those who were uninsured to buy insurance. Using tax penalties, as we did, or tax credits, as others have proposed, encourages “free riders” to take responsibility for themselves rather than pass their medical costs on to others. This doesn’t cost the government a single dollar."
As many have been maintaining, Romney's reasoning shows no essential disagreement with ObamaCare. Romney favors government compulsion in healthcare.