The Roman Empire: Regions of the Empire that were costly to occupy

Length is roughly 3000 words give or take in 12 point font, Times New Roman with MLA citation style. Online sources and hard copy books may be used. This is the essay topic:
“The Russian attack on Ukraine makes us think of the costliness of invasion and occupation. What region(s) proved particularly costly for Rome to occupy, and why were these exceptional?”
It may be useful to compare the Roman occupation and Russian invasion/occupation and how methods of doing so have changed.
Thank you and if you have any questions feel free to get in touch!