As far as I know, there are only two axis around which entities can rotate around, but I've seen some plugins (TrainCarts for example) which roll entities (minecarts/armorstand head). I know this is a very advanced topic and I know that you probably have to create a custom entity for that, but does anyone know how to achieve this?
Depends. There is a function which takes yaw and pitch, but not roll. The protocol also only supports yaw and pitch