The Roman Empire was not the final beast kingdom. The final beast kingdom, the kingdom which in the idol of man is the toes, partly iron and partly clay, partly strong and partly weak, is still to emerge. This final kingdom is described in Daniel 11 as being two kingdoms, North and South, that war with eachother and falsely unify by lies. Just as iron does not mix with clay, so the two kingdoms that make up the final kingdom of lies, shall not cleave to eachother.