when replacing front rotors

[So broke]

whats the deal on the front rotors do you have to replace the Hub Assy. every time you change the rotors? if not how do you tell if they are bad?

 

[Wwildman]

Would this be 2wd or 4wd?
If it is 2wd the rotor and hub are built together , My option would be mic the rotor thickness to see if they are below spec and have them machined if they check out good .But above all it you are reusing the old rotors do not mix up sides or bearing .
This is also a good time to clean and repack the bearing .

4wd are slip off and again I would mic them to see if they are below spec .If not you can machine them