Question

As the roman government became more efficient, it took on more functions. to pay for these services, rome ________.

Answer 1

Assuming this is referring to the Roman Empire, I would say that to pay for its new functions, it would have to increase taxes or tribute to pay for such things as an expanded military and the infrastructure involved in a vast empire (it contained 21% of the whole world's population at its peak). 

Answer 2

the answer to this question is increased taxes on farmers who lived outside of Italy
Larger government will always result in larger government spending (which will led into a higher amount of tax that must be paid). Since roman do not want its people to turn on them due to the increase in tax, Roman government decided to take it from the people outside their empire.