The way I see it there are two paths to staying informed in Rome. The first is the official path:

• An event happens and the Roman official on the scene is informed
• That official sends word to the Senate
• A magistrate gives an official address to the people (called a contio). He is inherently trustworthy because of his office.
• You know someone who attended and he gives you the news and you can weigh it against what other people tell you

The less official form goes as follows:

• An event happens abroad

• A merchant from the region goes to Rome and starts talking about it. Or a friend of yours sends you a letter (if you can read/live a life where you have friends so far away from home)

• This information spreads around the city and you probably hear it from different people and can weigh their accounts

• Finally the official dispatch will arrive and a contio will be held.

So regardless of the source, most Romans would be far removed from the event and thus incapable of making a solid judgment about whether his information was reliable. Did Tiberius molest children? Is there a Briton queen defeating Roman legions? Did Gaius have sex with Drusus last night? Does Tertius beat his slaves? They could ask their friends or maybe their patrons but there's very little chance they could verify it except if they go to a contio or a trial where the information is stated by an official. But then again Cicero never showed his evidence during the Catilinarian conspiracy except to the Senate. He just described the evidence to the people.

That depends on what you mean by 'reliable'.

There was profession of praeco, or newsreader, in Rome who would read out news bulletins to the crowds, like a modern news reader does today on TV. This was useful being that most of the Roman populace was illiterate, and no printing of any kind would exist in Europe for 1500 years.

The news would be very much sanctioned by the authorities, which brings to mind the old quote, 'I don't believe anything until it is officially denied by the government.'

I would imagine one of the best places for news (albeit of the internet gossip variety) would be chewing the fat in the forum.