This, as Roger would be the ruler of both Jerusalem and PalermoWhat would motivate either Roger or the Byzantines ally with one another, given their past conflicts? The de Hauteville's of Italy had usually been adversaries of the Komnenos dynasty since Roger Guiscard.
So, this TL would see Roger seeking the aid of Manuel I Comnenus (a crusade against Egypt), which could potentially affect the German involvement, under Conrad III, in the alternate Second Crusade (1145-49). The reason being that the Holy Roman Empire had interests in Italy, specifically about whom should be on the Papal throne. And the Papal States had to play both the Germans and the Normans against each other to preserve its autonomy.
And Manuel had a dream of re-union of the churches, a dream that he almost achieved with Pope Hadrian IV, but the Sicilians striked back and repelled the Romans off the Italian Peninsula. With Sicily-Jerusalem allying with Constantinople and a favourable Patriarch [of Constantinople], this might happen, since Manuel was a sort of 'conquering hero' for the people, claimed to be the ''most blessed of the Emperors''.