I'm kinda stunned to see a thread like this. I love RockAuto.
I had one defective part went like this "hi, i bought VVT cam actuator solenoid and right after the install, there was a CEL on my truck. I pulled the plug and there is a little oil in the plug, this may be a defective part"
The response was basically "okay, we sent a prepaid label to the email on your account, send it back in X number of days"
No hoops to jump through, they just accepted the return with no hassle.