MAGI is calculated differently for different purposes. There are about a dozen different definitions of MAGI, depending on what it is being used for.
The Modified Adjusted Gross Income Worksheet in TurboTax is for Passive Activity Loss Limitations, not for Roth IRA contributions. To calculate your MAGI for Roth IRA contributions use Worksheet 2-1. Modified Adjusted Gross Income for Roth IRA Purposes in IRS Publication 590-A. You will find other useful information about Roth IRA contributions in Chapter 2 of that publication.
