Why do they say pagare alla Romana?

Among the numerous famous expressions used in the city and in the whole country, one of them is very well-known, rich in debates about its meaning - the famous expression pagare alla romana that means to divide the bill among the friends or to pay just your order. Which is the right one? And why do they talk about Rome?

The meaning
Pagare alla romana, fare alla romana means to divide the common expense among friends - expense usually concerning a lunch or a dinner at the restaurant.
According to the literary tradition, this has not always been its original meaning. According to the Grande Dizionario della lingua italiana by Salvatore Battaglia, in 1700 and 1800, some famous writers such as Goldoni, Gozzi and Nievo used the expression alla romana to define the action of escaping (andarsene alla chetichella), giving a meaning similar to not pay the bill to the expression. Another occasion of the period connected with this expression was the sharing of a meal with other people sitting at the table, and this is more similar to the current use.
According to dictionary we mentioned above, there are no literary sources about the two interpretations of the expression, that probably means this passage took place among the common people, to come out lately with the new meaning.

Usual idioms and uncertain origins
Now you could ask why this expression is connected with Rome. Why Rome and its citizens are connected with the good habit of sharing expenses or escaping without paying or sharing food?
The connection is probably the popular tradition of people that used to have trips in the countryside, eating a lot, according to the common dictionaries that confirm the use of the term "romanata" to talk about a meal in the countryside.
The Grande Dizionario says "romanata" means meeting in which each participant pays a part of the whole expense, quoting just Ugo Foscolo and his letter "Lunedì verrò forse ha una romanata in campagna vicino a Fiesole con la compagnia delle signore Orozco", and remembering another document from 1800 - the Lessico dell'infima e corrotta italianità, by Fanfani and Arlia - telling about another definition used to talk about a lunch or dinner during which each participant pays a part.
Some people say this act is not very real, as it is very difficult to imagine the women of the time paying the dinner by themselves. Probably Foscolo used the term just to refer to the action of sharing food.

And how about the common people?
The literary Italian tradition offers no more about this topic, unfortunately. Fortunately, the web has a lot of ideas and different proposals about it.
There are many different points of view, but very difficult to be confirmed. One opinion is that the expression "fare alla romana" comes from the old tradition of the ancient trattorias of making the pilgrims pay the bill of the whole table, just dividing it for the number of people sitting there, and not according to what each one of them ordered.
Another idea is that the expression comes from a famous osteria, the Sora Pina: the owner of the place - with the same name - used to step on the customers feet by the broom stick as they got in the restaurant, to let them understand they had to pay regularly.
Another possibility is that this expression comes from the fact the food offered in that period to the pilgrims was very simple and it always had the same price, so everybody used to pay the same amount of money. Another story refers to the term “romano” considered as the weight of the stadera, the ancient scale, called "rumman". It used to slide on a graduated stick (called "stilo") ending with a plate to weight materials, characterized by the weighting system "alla romana".
But if we consider this hypothesis as correct, how can we connect it with the current meaning? common bill for all the customers is the opposite of an accurate measure. Moreover, there already was another expression to define this accurate way of acting: "alla genovese".

Other origins
Whatever the real origin of these expression is, it is very interesting to find the corresponding foreign expressions for the same meaning. In Russian, Romanian and Turkish languages, this expression becomes "to go German", while English people say "to go Dutch".
What is very interesting is that the way of paying in Rome or in Netherlands and Germany has the same problems of meaning.