Without knowing the details of your situation, I probably would leave the 457 where it is rather than roll it over and pay taxes now. The question is more going forward: should you invest in the Roth or 457?
That too will depend on the details of your situation (tax rate now, expected future tax rate, etc.)
Thanks to it being a 457 and accessible without the 10% penalty when you retire, it's not too harmful to have it there. Additionally with the Roth you'll be able to access the principal contributions without the penalty, and only gains after 59 and 1/2.
Hopefully, being Mustachian, you are saving more than 5k/yr., so probably the most prudent move is split contributions between the Roth and 457.
I don't know anything about Valic, what fees they charge, or anything like that, you should look into that as well.