QUESTION: Does your self-directed 401k plan allow Traditional IRA rollover to your Roth solo 401K?
ANSWER: You are confusing the 401k to Roth IRA direct rollover rules with the 401k rules.
In short, the traditional IRA would need to be rolled over to the pre-tax 401k first and then an in-plan conversion processed with the funds deposited in a Roth Designated account.
Feel free to call us to discuss further.
Thank you, RK in Colorado