I answered a question a while back about the (non)existence of a Roman "newspaper." That I think should more or less cover you, but appended to it I should point out the role of rumor at the lowest levels of society. Rumor and word-of-mouth was certainly the way the vast majority of the population of the Roman world learned of events even within the city itself. There's an interesting (if, in my opinion, largely incorrect) article by Ray Laurence about the role of rumor in politics in the late Republic that points out how much information was being spread around in the city by ordinary social interactions. This is generally how most people would learn of this or that event, by hearing it from somebody who was either there or had learned about it from someone who actually had been or who had read the alba. The filtering of information from the politically powerful down to the lower levels of society often allowed for a certain amount of manipulation of information, by recasting things in a certain light--this manipulation is discussed well in Morstein-Marx's book on mass oratory