>>17807336 (OP)Christianity never comes about, the Romans still become some form of monotheists though, educated Greco-Roman elites were already moving towards that direction before Christianity became popular among the masses.
Aurelian and Diocletian were already pushing to make Sol Invictus the one god. Constantine too was a Sol worshipper before converting to Christianity. So they would probably still organize a Roman church around one god.
Or, even more likely, some other prophet would fill the role Jesus did, as there was clearly an audiance for a new religion. So maybe someone would take various Greco-Egyptian mystic traditions (like Platonism that also believed in an abstract universal deity), simplify them for the masses, and then that would be co-opted by the Romans and become the basis of a church.