We know she appears to be an engineer for the resistance.
Rose: I work behind pipes all day
However, when Finn meets her she appears to be on guard duty to stop people from using the escape pods to abandon ship.
Rose: Can you believe I've had to stun three people already today?
Also when she's piloting the salt speeder she seems to do a pretty good job of staying alive and outlives most of the actual pilots.
With all this it appears that she is more than just an engineer, do we know what her actual job was?
Disclaimer: All quotes are from memory so they might not be 100% accurate.