I found this on the romatourismo site:

"ROMA PASS"

The ROMA PASS will be available starting from this coming April 21st on the occasion of the celebrations for the Birth of Rome.

The three days pass will entitle its holders free entrance to the first two archaeological sites or museums chosen and will offer a discounted fee to all the other attractions of the city. The Roma Pass will also include unlimited transportation on buses and undergrounds.

It will be possible to purchase The Roma Pass in all museums and archaeological sites, tourist information desks and ATAC ticket offices, travel agencies, hotels, exhibition premises as well as online.

Great news and timely for us. We arrive in Rome 23 April.

Thanks for info.

Elly