It seems that this Form 1099-R is reporting a nontaxable direct rollover to a traditional IRA, not a taxable rollover to a Roth IRA.
You'll need to contact the 401(k) plan administrator to see if they will correct the form to show the taxable amount in box 2a. However, if you had not requested that the plan administrator initiate a rollover to Roth IRA but had requested a rollover to a traditional IRA instead, the plan is unlikely to correct the form since they acted as requested. If the plan administrator refuses to correct the form, you'll need to prepare a substitute Form 1099-R showing the taxable amount in box 2a the amount from box 1 (minus any amount in box 5).
