Is Trastevere in Lazio a good central location to stay in Rome? How far is it from The Vatican, Colosseum and FCO airport?

Trastevere is surely one of the most beautiful places to stay in Rome but unfortunately it is not connected by public transport  as other places are (for example there is not a subway station). To move quickly you can use tram 8. Arrived at  Largo Argentina you can move using buses passing through Corso Vittorio Emanuele (especially the 40 express and 64) leading to the Vatican. To go to the Colosseum / Piazza Venezia area you have to take the same bus lines in the opposite direction. During the weekends the 8 tram service works till 3 am (is an exception for daytime bus lines that in Rome usually stop service at midnight). Then is replaced by bus N8 which covers the same path of the daytime line but reaches Termini station passing through via Nazionale and piazza della Repubblica. In any case, the city center is just beyond the river from Trastevere, and you can easily walk (10 minutes) to Campo de Fiori and Piazza Navona from there. Gianicolo is also very close, from where you can experience a beautiful view of the town. A public transport ticket (BIT) in Rome costs 1,50€ for 100min of validity. Using it you can take, during 100 minutes after obliteration, up to 3 means of transport in Roma Capitale area but it's valid for only one subway ride and it's not valid for the Fiumicino Airport train unless you use it to go from stations in the city. Depending on your holiday you can consider to buy a daily or weekly ticket or a Roma Pass (http://www.romapass.it) that also  gives you museums and events access. Using Atac (public transportation company in Rome) website http://www.atac.roma.it you can get all the informations about tickets, bus, tram, and underground routes. Using http://www.atacmobile.it in your smartphone you can also get real time information about public transport and waiting times for buses. The service is avaible every day from 6.30 AM to 12.00 AM. If you use an iPhone you can download "Roma Bus" free app from the AppStore. (It's an unofficial app but uses Muoversiaroma APIs)

The FCO airport is about 30-40 minutes outside the city.  It's kind of impossible to be in the center and near the airport.  The historic center of Rome is small and easily accessible.  You could cross it on foot in about 30-40 minutes.  Trastevere, if you're close to the river, is walking distance into the historic center.  The Vatican is to the north, but not all that well connected to Trastevere by public transport.  If you're west of Trastevere in Monteverde you'll need to take the tram into the center at Largo Torre Argentina, which is fairly quick and easy, and from there you can visit everything on foot.  The subway, if you're in Trastevere, is totally unusable, so it'll be buses, the tram and foot.  Getting in and out from the airport you need to get directions to Stazione Trastevere and not Termini.  If you respond with the address I can tell you if it's central or not.

Trastevere is a part of Rome (which is a city in Lazio which is a region of Italy), very picturesque, known for the night life (even if it's way more vital in summer than in winter for obvious reasons, you did't specify when you travel).While it's totally fun to spend some days in an area full of pubs and restaurants, it can also get quite noisy at Friday and Saturday evenings.It's not very far from the center (colosseum and so on) and from the Vatican, you can walk from there. However, since Trastevere is a renowned area in Rome, often hotels and people renting rooms or flats, write that they are in Trastevere even if they're just "quite near", so if you have the full address of your location look up the walking time on google maps.Also mind that while Trastevere is quite flat, the areas around are on small hills, which could make your walking from/to the apartment less enjoyable.Regarding the airport, the problem is not the distance but the connections. If you want to go by train, you'll have anyway to arrive to one of the main stations (Termini usually) and then move from there using busses or trams.However, Trastevere is inside the "fixed price area" for taxis from and to the airports, so you will pay 48€ no matter what (read : no matter how much traffic you find, or how much fantasy the taxi driver has .. and remember to ask taxi driver for the fixed price BEFORE they start, they have selective amnesia sometimes).

When I think of Rome now, I think of Trastevere. Along with Camp dei Fiori, it's my favorite part of Rome. Once you get all of the tourist stuff out of the way, make time for wondering around the tiny streets of Trastevere.

Viale Trastevere is quite a long street so it would depend where your B&B is actually located. As a rule of thumb, the closer you are to the river the better it would be for the locations you're interested in visiting. I'd say the Coliseum is a bit farther than you think, and if you are going to walk be prepared for a 20/30 minutes one at least. Also, be awar that FCO airport is outside the city so basically nothing that's in the city can be defined "not far" from it. A taxi ride to and fro it should cost you no more than 40€ - check the prices of the official white taxis and NEVER accept a ride from unofficial drivers.

If you are just visiting Rome for a few days and want somewhere central to all the sights and having a classic historic feel to it this is a great place. Depending on the time of day you arrive it will take you from 25-40 mins by cab from the airport or if you want to save some cash the train is very close (Trastevere Station). This area is full of restaurants and bars but is also very popular with tourists.