Converts...from Islam to Christianity?

[Fragony]

The (early) middle ages in Europe weren't nearly as bad for religious minorities as people like to think. Just about all major towns had thriving jewish communities and heretics were hardly prosecuted, that is about at the same time as the islamic golden age, prosecution of heretics was more political then religious little dispute between the HRE emperor and the Vatican.

http://en.wikipedia.org/wiki/Investiture_Controversy

that was because the romans had many harsh decrees against the jews so we hoped that by converting romans as much as we can, judaism would become more acceptable, thus having the oppressive laws removed.
after they saw it was hopeless they stopped.

Not really, jews were pretty much left alone, been revolts that were put down the roman way but romans didn't really care, they were traditionalists, as long as you payed tribute to the gods and later the emperor they didn't really mind that much. That is why christians were prosecuted, they refused to pay honor and the romans feared that would bring harm over the empire since it would displease the gods.