The Romans had nothing to do with the Sahara Desert. Neither did the Egyptians, which-predates the Romans, or even the great Mali Empire, which post-dates the Romans.
You still haven't answered my question on whether humans are supposed to eat plants.
We either eat plants directly,indirectly or die. I'm eating some of my homegrown sweet, tangy, crisp blueberries for breakfast as we speak.
"The word desertification was first used in 1949 by the French geographer Andre Aubreville to describe the change in North and equatorial Africa from productive savanna forest, grasslands, and shrublands into unproductive desert"
managingwholes.com