I've always used a Roma Pass at the Colosseum.but I am told that the line fron Tickets is shorter at the Via San Gregorio entrance to the Palatine which sell the combined tickets fot the Palatine and the Colosseum
For the Vatican buy ticket ahead of time online or go after 1 pm. The lines in the morning can be huge. The shortest amount of time that I have waited in the morning and got in was one hour and 40 min.
The Basilica is free and I have only seen a line to get once out of the 5 times that I have been there (not counting the X-ray security station.
I agree- Pallatine Hill entrance is a good bet.
And I've heard that Monday's are busiest at the Vatican- it certainly was when I was there. Buying tickets online was the best decision I made on the trip.
I just got back from a 3 day trip to Rome.
For the Vatican we decided to pre-book the night before and print off the slip using the Hotel's PC.
I really recommend you pre-book as it allows you to skip the VERY long queue!!
Although there is a fee of 4 Euros per ticket, it's definetly worth it when you see the length of the queue for the museum, and in the Rome heat, it'snot very nice.
Mhou was lucky to be able to prebook her tickets to the Vatican Museums the day before. They often sell out, especially at peak times. I would book those tickets several weeks ahead.
We brought the Roma Pass at the Ottaviano Metro for 25 euros each which gave us 3 days of a metro and bus pass and 2 attractions free. The Colosseum, the Forum, and Palatine Hill is considered all of one attraction if seen in the same day. We got to the Colosseum at 9:30and bypassed a very long line of people waiting to buy tickets. After lunch we went to the Forum and bypassed another very long line. The bus and metro pass was very helpful at night when we were visiting the palazzo and fountains. We did a lot of hopping on and off buses and if your not quite sure how to get to the metro by walking from your location the buses always seemed to go by some metro station. The metro is very easy to use with good signs pointed you in the right directions. There was always people around so felt safe even at night..Edited: 3:33 am, May 31, 2010
The combination Colosseum/Roman Forum/Palatine Hill ticket is actually good for two *consecutive* days, for one entrance to each site. (However, if you enter the Forum, you can pass internally to the Palatine Hill, and vice versa.) If you use a Roma Pass to enter, the two days must be within the 3-day validity period. That's three calendar days, so if you first use it late in the afternoon, your first day ends at midnight.
I just got back, I would say not to buy a Roma Pass, and to not prebook the Vatican is a huge mistake. You'll walk past a lot a lot of people in line who didnt do so. I had a Vatican 2 PM appt on a friday, i didnt wait one minute line! That said the Vatican was packed with large tour groups. I cant imagine what its like at its worst!
Castel Sant'Angelo costs 5 euros in theory, but there are often temporary exhibits there that raise the price to as much as 10 euros. The Colosseum is 12 euros, and single tickets on bus/metro (including transfers) are 1 euro apiece. I can't find whether there is a temporary exhibit at this time at the Castel Sant'Angelo, but if there is, the Roma Pass will pay off. If not, it will be close.