Amounts contributed to a traditional retirement accounts are deducted from income for taxes (to be tax as income when withdrawn). In a Roth conversion, the money from the traditional account is counted as income and taxed then placed in a Roth account to be withdrawn tax free during retirement. The loophole for early retirees is that after 5 years in the Roth, the converted funds can be withdrawn penalty free just like regular Roth contributions can at any time. I agree with others, that since you expect to be in a higher tax bracket at retirement, Roth may be the better choice right now.
BTW, if your 2015 income is low enough, it may save you a bit of money filing an amended return after funding a Roth if you can claim Saver's Tax Credit.