"Do I also need to deduct my self-employed health insurance"
For the purpose of having the earnings needed to support a Roth IRA contribution? No.
Deductible retirement contributions reduce the amount of self-employment net earnings available to support the self-employed health insurance deduction. Roth IRA contributions do not result in this reduction because such contributions are nondeductible. Your traditional 401(k) deferrals do reduce net earnings available to support the self-employed health insurance deduction. The net profit goes first to support the deductible portion of self-employment taxes, next to support deductible retirement contributions, then to support the self-employed health insurance deduction.
If your self-employed 401(k) provides a designated Roth option (likely it does because of recent tax code changes related to catch-up contributions for highly-compensated employees), you might consider making some of your 401(k) contributions as Roth contributions, allowing you to increase your Roth IRA contribution and perhaps your self-employed health insurance deduction. For example, if I have $8,608 of net profit from self employment, that would give me $8,000 of net earnings from self-employment after subtracting the deductible portion of self-employment taxes. That $8,000 of net earnings would support an $8,000 designated Roth contribution to the 401(k), an $8,000 Roth IRA contribution and an $8,000 self-employed health insurance deduction. The deductions on Schedule 1 would total $8,608.
However, depending on the amounts involved, making a designated Roth contribution to the 401(k) instead of a traditional deductible contribution could increase your AGI and affect your ACA credit.
