Direct from Carbotech FAQ section:
If you have had another manufacturers brake pads on those same rotors; then you will ABSOLUTELY have to replace or resurface (turn) those rotors before installing the Carbotech brake pads.

If the rotors and drums are in relatively good condition, meaning they are smooth, flat, with no visible cracks, deep scoring, distorted, and with no other visible damage; and you have ONLY had Carbotech brake pads on them, then they do not have to be resurfaced or replaced.

Carbotech XP20
The latest iteration of the highly successful XP series of compounds. XP20 is a step up from the highly successful XP16 compound. With an extremely aggressive initial bite, the most linear torque curve to date and excellent fade resistance the XP20 leads the highly successful XP series line of compounds from Carbotech. XP20 has a temperature range of 275°F to 2000°F+ (135°C to 1093°C+). Carbotech™ XP20 maintains our tradition of having the outstanding release and modulation that has made all other Carbotech compounds so successful. The XP20 as with other Carbotech compounds is very rotor friendly. Carbotech XP20 is NOT recommended for use as a daily driven street pad due to possible elevated levels of dust and noise.