I've always heard that the torture of the cross was invented in Rome.  I have always had some doubts of that, because the sophistication of the terrible torture that such a tool can inflict is the most  cruel and refined childbirth of an Oriental mind, and it's not something that originated from the practical mind of the ancient Romans.
The death of a crucified comes from a  scary mechanism: the open arms make it hard to breathe, while the weight of the body pulls down, practically blocking lungs.
Trying to breath, the crucifix pushes with legs leaning on the shelf  upon his feet, and then falls down from exhaustion. This succession of movements, the tremendous pain, and the anxiety cause at the end a heart attack  and the crucifix dies after a long agony. (° description from the book: 'the shroud true or false?' Maria Grazia Siliato)

SOME INFORMATION ON THE SYMBOL
The Camuna Rose. Of the cross we have some examples since the prehistoric Neolithic age (see aside the  camuna rose, found in the Camonica Valley, also famous because it is the symbol of the italian  region named Lombardy), but it's archaeological history dates back to ancient Mesopotamia; at first was the symbol of the Sumerian god, then of Tammuz, the god of Tyre's inhabitants. It was later developed into the so-called swastika, which was used in many other ancient cultures always to mean greetings or luck.

The Egyptian ankh (from the hieroglyph which means 'life') is the representation of god the Sun, that is of course, the primary source of life. 
In the Western culture, the Cross that we know comes from stauros (from greek: σταυρός) that is a pointed pole planted right and used for many different uses, for fencing, mooring posts, or piling to create foundations.  
For some Islamic cultures the cross has instead the meaning of wisdom, being composed of the two directions: the vertical one is the being  and the horizontal the doing, the first one is representing the Soul and  the other  Psyche and Matter. The center is the Heart. The verticality axis reflects the horizontality as the sky is reflected onto the sea.

THE CROSS' TORTURE, INVENTION AND USE
The inventors of the cross were Sumerians or most likely the Persians, the Greeks used it and surely took it because with Persians they clashed periodically. The Carthaginians punished they fleets' admirals with this method, if they were defeated in war or showed signs of independence; finally the cross has been adopted by the Romans, who came to know it probably during the Punic Wars.
The practic mentality of the ancient Roman judged it a terrifying ordeal, so scary to be reserved for those who were not Roman citizen, and in the case of serious crimes. For five centuries, the crucifixion was imposed in cases where the slaves rebelled and killed the owner. We all remember, I think, that after having completed a successful campaign of repression of the Third Servile War, under the command of eight legions against slaves and gladiators who had rebelled, led by Spartacus, Marcus Licinius Crassus did crucify survivors. Very rare thereafter were the rebellions of slaves.

THE CROSS' TORTURE, ABOLITION
It must be put in relationship to the 'Constitutio Antoniniana de civitate' of 212 dC, with which the Roman Citizenship was given to all the Empire's inhabitants, and because this kind of death or also the 'flagrum' one it could not be appled to a Roman citizen.
In the West, at the beginning of the fourth century, the Emperor Constantine the Great forbade public courts to condemn the crucifixion. But this practice lasted much longer in the East and in other countries; in this regard, there are detailed accounts of crucifixions still in the ninth century.

THE CROSS HAS BECOME AN UNIVERSAL SYMBOL DUE TO A HISTORICAL FACT.
The cross has become famous for a historical fact since the year 30 AC, while in Rome the emperor was Tiberius  and in Judea  was Procurator Pontius Pilate, when that Jesus of Nazareth, a man aged of 36/37 years, was crucified in Jerusalem at the request of the Jewish Sanhedrin. From that day on, the entire world was never the same..

As for the old prejudice against the Romans, that are the 'gentle' oppressors, now often some people do not neglect to lie, telling that Jesus of Nazareth was killed by the will of the Romans themselves, trying to unload a responsibility that instead it is solely to the Jews. I will discuss this in an article, titled "Pilate defended", because while the Orthodox Church has even sanctified him and his wife Claudia, in the West the Jewish influence, prevalent even in the Catholic Church, has made, wrongly, him to be a coward and abject.