Rooting isn't for everyone. You have to know what you are doing and find directions and follow then to the letter.
You can trip Knox, which voids your warranty or you could turn your phone into a basic expensive paperweight.
Only certain carriers running Lollipop on the Note 4 can be rooted. AT&T is not one, it has a locked bootloader that hasn't been cracked. I read about rooting for over a year before I ever did it and I still know very little about it. I just know to follow instructions to the letter on xda. I also know if people on xda say "the Note 4 Verizon can not be rooted yet" it can't be rooted and you will brick your phone trying.
Why do you not want Lollipop?