Boom lifts (more recently monikered as MEWPs) have gained significant rough-terrain capabilities in recent years.
Although scissor lifts (another discussion) are explicitly referred to being "rough terrain," articulating and telescopic boom aerial lifts are usually not, unless they're tracked. That's because OEMs have baked in some rough-terrain capabilities, within limits, in their basic designs, mainly with tire and steering options, extra ground clearance, and safety features.
The inherent safety issues that boom lifts face can be magnified on rough terrain.
In general, boom lifts aren't recommended for use on a hill or incline. The center of gravity is higher than other machines, which increases the risk of a tip over. It is possible to work on a incline, however if the operator does not exceed the recommended maximum slope with a safe working load.