Roberts, 52, is a breast-cancer survivor who underwent a bone-marrow transplant to treat the rare blood disorder, myelodysplastic syndrome, in September. She since has been recuperating at her New York home.
Roberts said last week her doctors want to make sure her vision is clear and skin feels OK when exposed to makeup and lights before clearing her to go back to work.
She also said it is important to see how her healing immune system responds to interaction with her co-workers.
ABC News said Roberts arrived for a dry run at the studio at 5 a.m. ET Thursday, after waking up at 3:45 a.m.
"What a thrill to be back at 'GMA's' Times Square Studio this morning and see the best folks in the world, my 'GMA' family," Roberts said. "I can't wait to get back to the anchor chair in a few weeks."