"I'm having to move up my schedule," People.com reported the co-anchor said at the beginning of Thursday's edition of the program.
Roberts, a 51-year-old breast-cancer survivor battling myelodysplastic syndrome, is to undergo a bone-marrow transplant. She is expected to come back to "GMA" after she recovers from the procedure; however, no specific return date has been announced.
"I am very blessed," she said. "Forty percent of Americans can't even take a sick day, and here I know that I'm going to have a job when I come back."
Roberts said she is leaving Thursday instead of Friday so she can fly home to Mississippi to be with her ailing mother, Lucimarian, as well as family members impacted by Hurricane Isaac, People.com reported.