This code-G Form 1099-R implies that you told the plan to roll the distribution from the traditional account in your 401(k) directly to the designated Roth account in the same plan (apparently not the case here since the money went to a different financial institution) or to a Roth IRA. Such direct rollovers are taxable. If you told the plan to make the rollover to a traditional IRA or to the traditional account in another employer's plan and actually deposited the funds into one of these types of traditional accounts, the plan needs to correct the Form 1099-R to remove the taxable amount.
If you told the plan to do a rollover to a Roth account but instead deposited the money into a traditional account, the Form 1099-R will not reflect that you diverted the funds to a traditional account. Since that's not an error made by the plan, they won't modify the Form 1099-R. Instead you'll need to create a substitute Form 1099-R (Form 4852) in TurboTax where you can explain to the IRS what you did to divert the funds.
