When it comes to rollovers, having two IRAs—one Roth and one Traditional—is often necessary if you're rolling over mixed 401(k) assets. Here's why:

1. Separate Tax Treatments: Traditional 401(k) contributions are pre-tax, and their rollovers need to go into a Traditional IRA to maintain their tax-deferred status. Roth 401(k) contributions are made with after-tax dollars, and rolling them over to a Roth IRA preserves their tax-free withdrawal benefit.

2. Compliance with IRS Rules: Keeping these assets separate ensures compliance with IRS regulations regarding the different tax treatments of Roth and Traditional accounts. Mixing these could result in unnecessary taxes or penalties.

Thus, if your 401(k) includes both Roth and Traditional contributions, rolling them into their respective IRA types is crucial for maintaining their distinct tax advantages.