I think it's important to distinguish between the blood libel and ritual murder accusations. They have different histories. I am not aware of Roman accusations of blood libel, but it's been pretty well documented that the first cases in Christian Europe were ritual murder in 11th century England, and blood libel in 1235 in Fulda, HRE. The go-to people on this are Gavin Langmuir and Deborah Jo Miller. Jo's stuff was a dissertation written at Cambridge, while Langmuir has published extensively.
The blood libel was the belief that Jews drank the blood of Christians at Passover. The ritual murder accusation was the belief that Jews crucified Christian boys. Both are clearly projections about Christian beliefs.
Preachers were able to whip up frenzy against Jews, especially during Holy Week, by making reference to these spurious charges. Ronnie Hsia wrote a book on the Simon of Trent case, which was whipped up by that lovely Franciscan Observant preacher, Bernardino da Feltre.
And, in Poland, there were ritual murder accusations as late as the early 20th century. Interestingly enough, the ritual murder accusation surfaced against Muslims during the Bosnian conflict.
Some things never go away.