If you have no traditional IRAs with a nonzero balance, ask the IRA custodian to recharacterize the Roth IRA contribution. They custodian will transfer to the traditional IRA the amount originally contributed to the Roth IRA adjusted for attributable investment gain or loss. You can then do the Roth conversion of the entire balance in the traditional IRA that you were originally intending to do. If there was an attributable investment gain, the gain will be taxable upon conversion.
