That's a bit of hassle to set up right though. If you're using a mod that has Ply's mod integrated in it, like PBUM, you can do the following.
You have to set a variable to the entity's y angle before you rotate it to the player, and when you want it to rotate back, rotate the entity on its y-axis back the way it was using the saved value in the variable.
example code:
:state=0,dimvar=EntAngY,setvar=EntAngY EAY$,state=1
:state=1:rotatetoplr,etimerstart,state=2
:state=2,etimergreater=2000:entityangley=EntAngY,suspend
note:I'm not sure about the "EAY$" part, you'll have to look in the Ply's Mod manual.
