Rome is said to have more than 1.000 churches itself. Visiting 3 churches per day it would still take a year to see them all!
Most of the masses are celebrated in Italian (or rarely in Latin), but if you are looking for English Masses in Rome you have plenty of churches where you can attend.
Here below the most well known churches in the city center of Rome with full address, area, phone number and mass schedule (mass schedule changes frequently and with seasons, please make sure to check for a updated/detailed schedule before attending).
Santa Susanna Church (American National Church) Address: Via XX Settembre 15 (Via Nazionale/Termini Station)
Phone: 06 420 14 554
Sunday Masses: 6PM (Saturday) 9 and 10:30 AM.
http://www.santasusanna.org
The Church of St. Sylvester in Capite
Address: Piazza San Silvestro (Via del Corso / Spanish Steps Area)
Phone: 06 679 7775
Sunday Masses at 10 AM and 5:30 PM
http://romanchurches.wikia.com/wiki/San_Silvestro_in_Capite
The Pontifical Irish College
The residence for Irish seminarians in Rome
Address: Via SS. Quattro 1 (Colosseum Area)
Phone: 06 77 2631
Sunday Mass: 9:30am (Sept-June)
http://www.irishcollege.org/
St. Patrick's Church
Irish National Church
Address: Via Boncompagni, 60 (Via Veneto Area)
Phone: 06 420 3121
Sunday Mass at 10 AM.
http://www.stpatricksrome.com
Church of St.Ignatius of Loyola
Address: via del Caravita 8a (Pantheon Area)
Phone: 06 679 440
http://www.chiesasantignazio.org/en/
Caravita: The Oratorio of St. Francis Xavier
An international Catholic community in Rome
Address: Via del Caravita 7 - next to S. Ignatius of Loyola (Pantheon Area)
Sunday Mass: 11am
http://www.caravita.org
The Venerable English College
The residence for English seminarians in Rome
Address: Via Monserrato 45 (Campo de Fiori Area)
Sunday Mass: 10am
http://www.englishcollegerome.org
All Saints' Church
Anglican
Address: Via del Babuino, 153B (Spanish Steps Area)
Phone: 06 360 01 881
Sunday Masses at 8:30 and 10:30 AM
http://www.allsaintsrome.org
Rome Baptist Church
Address: Piazza San Lorenzo in Lucina, 35 (Via del Corso / Spanish Steps Area)
Phone: 06 687 6211
Sunday Mass at 10.30 AM in English
http://romebaptist.org
St. Paul's Within-the-Walls
Episcopal
Address: Via Napoli 58 (Via Nazionale/Termini Station)
Phone: 06 488 3339
Sunday Masses at: 8:30 and 10:30 AM, 1 PM in Spanish
http://www.stpaulsrome.it
Ponte Sant'Angelo Methodist Church
Address: Via del Banco di Santo Spiriti 3 (Castel Sant'Angelo/Navona Area)
Phone: 06 686 8314
Sunday Mass at 10:30 AM
http://www.methodistchurchrome.com/
St. Andrew's Church of Scotland
Presbyterian
Address: Via XX Settembre, 7 (Via Nazionale/Termini Station)
Phone: 06 482 7627
Sunday Mass at 11AM
http://www.presbyterianchurchrome.org