In "The Gallic Wars" Caesar describes the use of a siege tower to gain a hight advantage over the defenders on the wall which would then be used to attack them with missiles. I was under the impression that a siege towers main purpose was to provide a way to scale a wall. Was that just an exception that was popularized by movies like LOTR? How often were siege towers used in the way Caesar described? What was the basic philosophy on how they should be used?
While, I cannot comment specifically on how Roman armies used siege towers, I will say that their role in scaling walls is not just fiction. This earlier answer by u/valkine u/pinguis and others highlight how siege towers were used in the medieval era.
To add to what was mentioned in the linked post, we can have a look at how illustrations in manuscripts depicted siege warfare. Below are a couple depicting the 1099 Siege of Jerusalem. Now, these illustrations were created hundreds of years after the fact, so don't take them as an accurate depiction of how the siege towers actually appeared in 1099, but rather as evidence that siege towers were indeed used to scale walls.
From Guillaume de Tyr's Historia (possibly 14th century)
Possibly from Sébastien Mamerot, Les Passages d'oultre mer (14th or 15th century)
