Can rooting be the cause of battery drainage?
Short answer: No

Long answer: It's all the apps and services running in the background, some great apps I use for monitoring what's going on with the phone: 


System Panel [theres also a lite version, SystemPanelLite Task Manager]
CPU Spy
BetterBatteryStats


With those you will be able to narrow down what is causing all the battery drain

Also it may be wakelocks on your kernel