Rollovers: Traditional TSP with non-taxable

Hello and thank you for your time.

I recently separated from the military and I have a Traditional TSP with a portion that is non-taxable (I was in a tax-free zone for a few months years ago). My plan was to rollover the taxable portion to a Traditional IRA. However, I found that the non-taxable portion will be on a separate check. Will I be taxed if I roll that portion over to a Roth IRA at a different institution? Thanks in advance.

On another note, the reason for the rollover is because I'm not sure if I'm going to be working at another federal job, so I want to continue to contribute to what I earned via the TSP.