The "GMA" anchor and breast-cancer survivor is battling myelodysplastic syndrome.
Roberts, 51, said Thursday she will take a medical leave in late August or early September to undergo a marrow transplant. It is unclear how long she will be gone.
"It's fascinating-slash-scary how to prepare yourself for something like this," the New York Daily News said Roberts told reporters in a Los Angeles press conference she participated in via satellite from New York.
Notable deaths of 2014 [PHOTOS]
'True Detective' adds Kelly Reilly