I'd be willign to bet that Persia, arabia, and ehtiopia 9which opens up the res tof eastern africa) would all convert to christianity- it was close enough to persian religion such as -persian- (Roman mithraism seem smore and more like an entreilly different religion from what the Persians practiced, and had a different official name to boot) mithriasm, to make it a fair choice for persian converts, and close enough to judiasm to make the jewish poulation in arabia, and ethiopia -far removed form the center of judiasim in jeruslam- possible converts.
meanwhile, the roamns own psuedo-monothesitic religion of "Roman mithraism", under the soldire god sol-invictus fo rth emen, and the goddess of isis for the women folk gain promience... imagine, 1492 columbus sails the ocean blue, and lands in the americas righ ton cue, but istead of preachers coming as well, it will be mithraic temples atop pyramids to be built over there