Remember that income tax is due upon withdrawal, and withdrawals from your 403(b) account prior to age 59½ are subject to federal restrictions and may be subject to a 10% federal early withdrawal tax penalty.
The 10% penalty also applies to the amounts rolled over to the 457(b) plan from non-457(b) eligible retirement plans.
Qualified distributions from a Roth account are tax-free. Generally, a qualified Roth distribution is a distribution that (1) is withdrawn after the end of the five-year period beginning with the first year in which a Roth contribution was made to the plan, and (2) is after age 59½, death, or disability.