I get the same increase in tax due when I enter that it will be a Roth contribution, which one would expect to pay taxes on... maybe there's a bug in TurboTax?
Are you getting a warning that you have an excess contribution at the end of the IRA contribution interview? If yes, then it seems as if you are not having enough taxable compensation to make the contribution. If you are self-employed, compensation is the net earnings from your trade or business reduced by the total of:
For 2021 the total contributions you make each year to all of your traditional IRAs and Roth IRAs can't be more than:
Your traditional IRA contributions may be tax-deductible. The deduction may be limited if you or your spouse is covered by a retirement plan at work and your income exceeds certain levels. Please see IRA deduction limits for details.
Do you have a profit (not just income) from self-employment?
The result indicates that you have no compensation (or insufficient compensation) to support the contribution. If your only compensation is from self-employment, your IRA contribution is limited to your net profit minus the deductible portion of self-employment taxes.