I don't know a lot about Rome...I live in Milan and I can tell you Elvis is popular in Italy but not as much as in USA (obviously ).
He sure have many fans here and he influenced our music too.
There are many places and events in Italy dedicated to him...in Milan there's a pub called "Memphis Cafč" dedicated to Elvis...here's the link of the site where you can find info:
In Padova, for example, there's a shop that sells only Elvis stuff :
I hope there's someone here who lives in Rome so that you can have more info