Ideally you would have a Form 1099-R that had in box 2a the taxable amount of the Roth conversion. Because the error was not theirs, Schwab will almost certainly decline to change the Form 1099-R. You could enter a substitute Form 1099-R which will give you the opportunity to provide explanation as to why the rollover was actually taxable. You could also just enter the Form 1099-R as is but making sure that box 5 has a number in it even if it is zero, then indicating to TurboTax that the rollover was to a Roth IRA. Doing so will cause TurboTax to treat the rollover as taxable, but the IRS might question this reporting (although the IRS often doesn't mind seeing too much taxable income being reported).
