Trajan was saved by hope and Ripheus by faith even though they did not know of Jesus. This is one of the more complex points in Dante's theology, as he appears to believe that Christ is not a sine qua non for salvation: rather, Christian virtues are, and while these are almost always found in Christ, it is possible to find them elsewhere.
- Yes: Jesus did not come out of nowhere (like Venus appearing on the beach). There was a foundation (prepared by God, apparently) for people to understand and accept him. The Greco-Roman empire was 'ripe for the picking', with Greek philosophy having much in common with Christianity (or at least providing a basis for intellectuals to get a theological upgrade). Even Greek mythology contains moral lessons on which Christian teachers can ride piggyback.