Like most questions about Roman history, the answer depends on the era you're considering.
In the early days of the Roman Republic, public taxes consisted of modest assessments on owned wealth and property. The tax rate under normal circumstances was 1% and sometimes would climb as high as 3% in situations such as war. These modest taxes were levied against land, homes and other real estate, slaves, animals, personal items and monetary wealth. Taxes were collected from individuals and, at times, payments could be refunded by the treasury for excess collections. With limited census accuracy, tax collection on individuals was a difficult task at best. UNRV
The same source points out that tax farming supplanted tax collection by 167 BCE The government privatized the collection of taxes, and sold the privilege to the high bidder.
Absent a solid census, the first system was prone to missing taxes and the second system was prone to mind numbing corruption and oppression.
In the early Empire, Augustus returned to direct taxation
Tax farming was replaced by direct taxation early in the Empire and each province was required to pay a wealth tax of about 1% and a flat poll tax on each adult.
Diocletion centralized taxation (moving the responsibility from provinical governors to a central bureaucracy) and resorted to manipulations of the money supply. His efforts are still used in econ courses as an example of really stupid behavior by the government
n the early Empire (30 BC- AD 235) the Roman government paid for what it needed in gold and silver. The coinage was stable. Requisition, forced purchase, was used to supply armies on the march. During the third century crisis (235–285), the government resorted to requisition rather than payment in debased coinage, since it could never be sure of the value of money. Requisition was nothing more or less than seizure. Diocletian made requisition into tax. He introduced an extensive new tax system based on heads (capita) and land (iuga) and tied to a new, regular census of the Empire's population and wealth. Census officials traveled throughout the Empire, assessed the value of labor and land for each landowner, and joined the landowners' totals together to make city-wide totals of capita and iuga. The iugum was not a consistent measure of land, but varied according to the type of land and crop, and the amount of labor necessary for sustenance. The caput was not consistent either: women, for instance, were often valued at half a caput, and sometimes at other values. Cities provided animals, money, and manpower in proportion to its capita, and grain in proportion to its iuga.[notes 13] Wikipedia.
Returning to the question - the tax rate you paid depended on when you lived, your social relationship with the tax collector, and a host of other factors. In the period cited in the article (circa 66 AD), taxation was by tax farming. I suspect that anyone who would rather be subjected to tax farming than US Taxation is relying on their skill in evading taxes. No matter what accusations are levied against the IRS, they are less abusive than tax farmers. It would be interesting to ask a Marxist historian to analyze tax farming and exchange entitlements; might be one place where the Marxists and the Libertarians would align (They would also argue ferociously against the notion that they align).