If my Gross Distribution for my 1099-R is contributions only - not gains - how do I indicate this on the form? Whic Box 7 code provides this context?

There is no Box 7 code to indicate that your Roth distribution is basis.  Roth distributions are considered as basis first, then earnings, but you have to tell the program what your basis is, unless you did that when you made the contributions.  To report your Roth basis in TurboTax Online, log in to your tax return:

• Click on Search
• Type in "IRA Basis"
• Click on "Jump to ira basis"
• Select Roth IRA (even if you are not reporting a 2024 contribution)
• Answer accordingly to "Did you make Roth IRA contribution for 2024?"
• Answer Yes to "Did You Open a Roth IRA Before 2024?"
• Answer Yes to "Would you like us to track your Roth IRA basis?"
• Continue and enter your Roth IRA  contributions made prior to 2024.

Once you have entered your basis, enter your Form 1099-R (if you haven't already).  If your basis is greater than your distribution it will be treated as a tax free distribution of basis.  Be sure to continue through all the questions after entering your 1099-R, by clicking on Continue.