Did the Romans invent the Battering Ram?
The Romans did not invent the battering ram, rather it was the Assyrian Empire. Tudiya was the first king of the empire.
A scaling tower was used in ancient wars to allow soldiers to reach the top of an enemies' town or fortress walls. If a battering ram is attached to it, then scaling the walls over an entrance to a fortress or city plus using the battering ram to break open the forts doors can be accomplished. This type of war "machines" were used into the Middle Ages.
As a device intended to knock down a sealed door of some kind, a battering ram is indeed a simple machine; or, at least, it can be. For, while sophisticated battering rams have been created and utilized, the trunk of a tree can serve just as well, when and where the gate or gateway to be rammed open is appropriately sized.