When you enter the 1099R, TurboTax will ask if rolled into a Roth account and you will answer "yes: and that "all" is rolled over to Roth and them it will be taxable event if coming from a Traditional (non-Roth) 401K.
To enter pension and annuity Payments (1099-R)
• Click on Federal Taxes
• Click on Wages and Income
• Click on I'll choose what I work on (if shown)
• Scroll down to Retirement Plans and Social Security
• On IRA, 401(k), Pension Plan Withdrawals (1099-R), click the start or update button