But fellow midfielder Chris Farrell is fit for the Stadio Olimpico clash after overcoming a knee injury.
Farrell starred in Ireland's 22-13 win away to Scotland earlier this
month but limped out of Munster's Pro14 clash against Southern Kings on
Rhys Ruddock misses out through hamstring trouble, however, and Will Addison is sidelined with a minor back complaint.
"Garry Ringrose and Rhys Ruddock will continue their respective
hamstring rehab at Leinster this week," the Irish Rugby Football Union
(IRFU) confirmed in a statement issued Tuesday.
"Chris Farrell has been reviewed by the Ireland medical team and is fit to train today.
"Will Addison has some lower back stiffness that is being managed at Ulster this week.
"Iain Henderson and Tadhg Beirne, who were named in the initial Six
Nations squad, have joined the group at Carton House this week."