No, no major specific incidents, at least that see Roma on the side of the attackers. The fact is much simpler: they were Europe's leading nomadic people and therefore seen as hopelessly different from the predominant urban and agrarian civilization. So were the peoples of the Eurasian steppe to all neighboring civilizations, even though the Roma never had significant military power.

The Roma arrived in Western Europe toward the end of the Middle Ages from India. And because of their nomadic style, they were always considered alien to the predominant European-Christian-urban civilization, thus viewed with suspicion, especially in a very closed society in which the city gates were closed at night and only residents could stay inside. They lived as itinerant artisans, specializing in the care of horses and metallurgy, as well as in circus performances and reading the future in cards or on hands (another suspicious practice liable to witchcraft). And it is useless to deny they also survived through stealing and swindling the settled populations. They were, as were the Jews, the perfect scapegoat to be punished whenever things went wrong.

Between the eighteenth and nineteenth centuries things got much worse. The Enlightenment rulers became convinced that it was their duty to "save" the Roma from a way of life and culture considered archaic and undignified, even against their will. With the 19th century and the rise of nationalism as the bonding of states, the Roma (again, like the Jews) were seen as a different people and thus "infiltrated" the "legitimate" local population. In short, if France is the land of the French, those who are not French cannot be in France. Repeat for virtually all European states. Moreover, industrialization and the gradual disappearance of "free lands" has deprived them of their most peaceful means of livelihood, impoverishing them and pushing them more and more into theft and other illicit livelihoods. Who needs a good farrier if everyone rides around in automobiles?

Today Europe's problem with Roma has not yet been completely solved and they are probably the most discriminated ethnic group on the continent: even progressive people without any problem with blacks, Muslims or queers, would have difficulty accepting Roma as a neighbor, because they are seen as inevitable carriers of illegality and degradation. Obviously this does not help their emancipation and a vicious circle is created in which the more they are discriminated against, the more they have to indulge in illegal activities, the more they are discriminated against ...

There is also a problem of ghettos. Basically the Roma are allowed by the authorities to live in "Roma campsites", areas reserved for them for the parking of campers and caravans. In theory it is made to respect their nomadic lifestyle, in practice they often become lawless areas with negative repercussions on the surrounding inhabited areas, from which other prejudices, other distrust, other hatred arise.

P.s. I'm sorry if my writing seems to reveal unwitting racism. Unfortunately, I am writing from Italy, which is considered the European country in which the social condition of the Roma is more difficult and the racism against them is more widespread, over 80% of the population according to some research