The Roman Senate played a critical role in the transition from Republic to Empire by gradually losing power while emperors like Julius Caesar and later Augustus centralized authority. Initially, the Senate held significant political influence, advising leaders and controlling budgets. However, as military leaders seized control, the Senate's dominance waned, culminating in the Imperial system where emperors had the final say in governance. This shift marked a substantial change in the Roman political landscape, moving from a representative system to autocratic rule.