Is the Roma Pass worth it?

Only if you plan on entering more than three major museums and using the metro frequently. For most, booking individual tickets is cheaper and more flexible.

How do I get from the airport to the city?

Take the Leonardo Express train from Fiumicino Airport to Termini Station. It costs 14 euros and takes 32 minutes.

How to See Rome in 3 Days Without Wasting Time

Prioritize one major site per morning and book 'skip-the-line' tickets at least four weeks in advance. Stick to a single neighborhood each afternoon to minimize transit time and prioritize walking over the unreliable bus system.

Book timed-entry tickets online. Do not show up at the Colosseum or Vatican Museums hoping for a ticket. Buy them on official websites (CoopCulture for the Colosseum; Vatican Museums official site) exactly 30–60 days before your trip.
Map your route by density. Cluster your sightseeing geographically. Do the Ancient Rome area on one day, the Vatican area on another, and the historic center (Pantheon/Piazza Navona) on the third.
Skip the public buses. Rome's bus system is prone to massive delays. Budget for taxis (FreeNow app) or simply commit to walking. Most major sites in the center are within a 20-minute walk of each other.
Eat away from the piazzas. Never eat at a restaurant with a 'menu touristico' sign or a waiter standing outside. Walk three blocks into the side streets of Trastevere or Monti to find authentic food at half the price.

Is the Roma Pass worth it?: Only if you plan on entering more than three major museums and using the metro frequently. For most, booking individual tickets is cheaper and more flexible.
How do I get from the airport to the city?: Take the Leonardo Express train from Fiumicino Airport to Termini Station. It costs 14 euros and takes 32 minutes.