If you are under age 59-1/2, no one has those records but you, or maybe your broker (the IRA custodian). The IRS does not keep those records more than 10 years. The tax law says that you are not entitled to any tax break you can't prove, such as tax-free Roth withdrawals. If you are audited and can't prove your contributions, the IRS gets to decide what is taxable.
However, if over age 59-1/2, you should not need to know your contributions, since all your withdrawals are tax-free at this point.
