[jackwashere]

The specs for 10/2 UF romex is 30 AMPS and 600 volts. Do amps ratings always pertain to the voltage rating for a given wire 600V or do they pertain to 120V?

 

[k_buz]

Up to 30 Amps, Up to 600 V, you cannot exceed either.

 

[mpoulton]

The current rating and voltage rating are unrelated. There is no trade-off between them, if that's what you're asking. The current rating is based on the diameter of the wire and the temperature limits of the insulation. The voltage rating is based on the dielectric strength of the insulation.