Through the end of 2014, an individual may rollover each IRA he or she owns into a new IRA one time and avoid paying tax on the rollover(s). Beginning in 2015, all IRAs owned by the taxpayer will be treated as one IRA for tax-free purposes. Therefore, only one tax-free rollover will be allowed in future tax years. Rolling over multiple IRAs will create taxable events.
For full details, visit the IRS website http://www.irs.gov/uac/Newsroom/IRS-Clarifies-Application-of-One-Per-Year-Limit-on-IRA-Rollovers-Allows-Owners-of-Multiple-IRAs-a-Fresh-Start-in-2015