I have had all 4 of my rotors off. It is a fairly straight forward job.
NOTE: If you are installing new REAR pads and you need to retract the rear caliper pistons, the process is a little different because of the Electronic Parking Brake (EPB) that is attached to the rear caliper (see yellow arrow below). This is my 2020 Bolt rear caliper removed from the car (brake line still attached)...
View attachment 43708
If you retract the caliper pistons, I think you have to go through some sort of calibration process when you re-connect the caliper to the car. You basically need to tell the car's computer "hey...I moved the caliper pistons."
(edit - Go down to post #15 for more info on this) I did not have to do this in my case because I just put my original rotors back on with the original brake pads. I didn't have to touch the caliper pistons.
Check
THIS post for a quick lesson on how to disconnect the EPB connector from each rear caliper. It's simple...but this might save you a little frustration if you haven't done it before. You absolutely
have to disconnect the EPB connector to remove each rear caliper.
I have a few more tips I will post in a little bit. I gotta start looking like I'm working.