Ronaldo spent the majority of the COVID-19 lockdown period in his native Madeira and returned to Turin on May 4.
According to Italian regulations, those returning to the country spend a further two weeks in quarantine, before being able to leave their homes.
Clubs are now awaiting the green light to resume collective work and, until then, will continue to train individually as they have done for the past two weeks.
There has been no Serie A fixture since March 9.
Juventus lead Lazio by one point and third-placed Inter by nine points.