Maybe post #3 here can give a little background:
https://forums.unrealengine.com/showthread.php?62854-Creation-of-crazy-rotations-amp-poses-for-intense-melee-combat-attacks
[EDIT]
if you say what you are trying to do then maybe you can get some advice.
Do you want to compare 2 rotations or interpolate, or …?
Do you limit it to yaw-only rotations or real complex rotations?
[EDIT2]
If you just want it in range 0-360 then just add 360 and do a modulus on that by 360 and it will get fixed (unless you have negative rotations beyond -360)
return FMath::Fmod(yaw+360.0f,360.0f)