This is a question for your 457(b) plan administrator. I suspect that you'll find that the exception to the early-distribution penalty for separation from service in or after the year you reach age 55 (or age 50 for public safety employees) only applies to a distribution from the plan of the employer from which service was separated and once rolled over the 457(b) that exception no longer applies. Such amounts rolled over to the 457(b) and the earnings thereon are required to be tracked separately from the other 457(b) contributions and earnings so that any early-distribution penalty can correctly be applied to distributions of the rolled-over amounts, but I doubt that your age at separation from service with the previous employer is known or tracked by the 457(b).
The 457(b) might also have restrictions on obtaining any in-service distributions at all before age 59½.
