Complex sentence: At the death of the monarch, under Emperor Augustus the empire of the Galatians was annexed by the Imperium Romanum as the province of Galatia.
Split into simpler sentences: At the death of the monarch, Galatia was incorporated as a province in the Imperium Romanum. Under Emperor Augustus the empire of the Galatians is annexed by the Imperium Romanum as the province of Galatia.