Roberts can basically go and confront her, and say that if she’s not there for oral arguments, then it would be difficult for her to relate to the case. This has been a continual problem for the court because they’ve had various people who had surgery or health issues, and they were gone for a week here, a month there.
I read a piece several years ago where someone suggested that a ‘extra’ Justice should be on the staff and fill in when these health issues pop up.
No Chief Justice would do as you wish. Justices are almost independent operators in this system.