After doing learning about the early history of Christianity, I learned about Saturnalia, which is thought to be a major influence on the celebration of Christmas. Before these holidays were infused together, what was the celebration of Christmas like? As in what traditions were used then as opposed to what traditions are used today? Additionally, what traditions have persisted throughout Christian history?
This isn't quite a response to your actual question because the question has some embedded assumptions that probably need to be addressed first.
Most modern Christmas traditions (which are variable globally) are nowhere near as old as Rome and have nothing to do with Saturnalia.
u/KiwiHellenist has given good answers to this before but the search function is hard to use on mobile, but this is similar content from his personage blog: http://kiwihellenist.blogspot.com/2015/12/christmas-and-its-supposed-pagan-links.html