The code G (combined with no other code) in box 7 indicates that the distribution came from the traditional account in the 457(b), not from a designated Roth account in the 457(b). Perhaps this Form 1099-R is reporting a distribution of employer matching of profit-sharing contributions and earnings thereon, which would explain why nothing is present in box 5.
A rollover from the designated Roth account in the 457(b) to a Roth IRA would have been reported with code H in box 7 of a separate Form 1099-R. If you received no such form, perhaps any money you had in a designated Roth account in the 457(b) is still in the designated Roth account in the 457(b). Either that or the money was taken out you pay pre-tax and deposited into the traditional account in the 457(b) despite your wishes.
