Here is my list of popular Catholic churches in Rome for your wedding. I have included some images and all the contacts for them all. Of course there are lots more than I have listed here but these are the ones I seem to find myself at most. If you click on the names they link to the websites of the churches.
St.Isidore’s College, Rome
Via Degli Artisti, 41
00187 Roma, Italia.
The contact priest is Father Michael MacCraith.
Piazza San Silvestro,
00187, Rome, Italy
E-mail : email@example.com
The contact priest is Father John Fitzpatrick S.A.C.
Irish College and?The baptistry of St. Johns Lateran Roma.
Pontificio Collegio Irlandese,
Via dei Santi Quattro, 1,
00184, Roma, Italy
Contact: Alison Mills
St. Patrick’s in Rome
Mailing Address: St. Patrick?s, Via Piemonte 60, Rome 00187
Church Address: Via Boncompagni 31, Rome 00187
The contact priest is Father Tony Finn OSA.
The Church of Santa Susanna
Via Venti Settembre 15
00187, Roma, Italia
The contact priest is Fr. Greg Apparcel.
Basilica Di Santa Maria In Trastevere
Piazza S. Maria in Trastevere
San Giorgio in Velabro
Via del Velabro 19,
00186 Roma Italia
Santissimo Nome di Maria al Foro Traiano
Piazza Foro Traiano, 89,
Other churches you could look at are, Church of Saint Anne in Vatican and Cappella del Coro (Chapel of the Choir) at the Vatican.