Slightest idea how to save/read rotation of enemy and update it to minimap ?

The UI minimap was essentially an experiment so my knowledge on translating all that kind of info is limited. I'd have to look into it more to give you a definite answer. Sometimes people fake the UI minimap by using 2D icons right above the player's heads that only appear on the minimap camera. It's a bit of a cheap effect but it works. Here is an example of what Unity did for a similar minimap: https://unity3d.com/learn/tutorials/topics/graphics/adding-minimap-icons