KingTumTum101 s approach seems legit to me.
And if you dont use root motion you can use a timeline and rInterpConstant to slowly rotate your actor to the new rotation.
Heres a quick and dirty non-root-motion solution I just made:
Its by far not the cleanest solution I guess, but it works very well already and it looks like in the video. Im hope itll point you the right way. Also im open to suggestions and hope someone can give some feedback.
The [turning] varialbe along with the [iMovementDirection] variable are then used in the animBP to trigger the turn state on and off.
https://dl.dropboxusercontent.com/u/25584030/ue4inplaceTurnGraph.PNG