Most vehicle manufacturers recommend inspecting the brake rotors whenever the brake pads are replaced. In many cases, replacing the rotors at the same time as the pads provides the best braking performance, promotes even pad wear, and helps prevent issues such as brake pulsation caused by worn or uneven rotor surfaces.
Brake rotors also have a minimum thickness specification. After one or two sets of brake pads, many rotors will have worn close to or below this limit and should be replaced rather than reused. Always inspect the rotors for thickness, excessive wear, heat damage, and surface condition, and replace them if they do not meet the manufacturer's specifications.