Did the European kings know the world was round in the 700s?

Do an image search of king Charlemagne. He lived in the 700s. He is clearly shown holding an "Orbis Terrarum" in many of the pictures. This is a sphere that is supposed to represent the whole earth. But I was under the impression that people in the Middle Ages thought the earth was flat. You could even get burned at the stake for heresy for thinking otherwise.

So what is a dark-ages king doing with a spherical earth in his hands? Was this esoteric knowledge of the elites while the peasants were the ones who thought the earth was flat?