I want to put paved roads in Briton. Well, actually, I already have, but instead of showing me a paved road and a description as it would when I take over a roman city, it shows a barrack building and warns me that the message should never be shown.

How do I get it to show the basic paved roads picture and description?

PS: I don't want to download a huge mod that will make hundreds of changes to my game, I just want functional paved roads in briton.

PPS: I don't care about realism, but realistically the British could have learned to build paved roads through trade, they were pretty civilized for "barbarians" after all. Even Rome considered them civilized.