Robin Roberts -- Testing the Water for 'GMA' Return

Robin Roberts returned to the NYC set of "Good Morning America" this morning -- the first time since undergoing a bone marrow transplant surgery -- for a private "GMA" test run to see if she's physically ready to come back to the show.

Just last week, Roberts explained that she would be doing a series of doctor-approved "dry runs" before officially re-joining the show.

"My doctors want me to see how many people I actually come in contact with," Roberts said ... "How my body reacts to the stimulation, that's code word for stress, of being in the studio environment."

She added, "My skin is very sensitive and so we have to see how it reacts to the studio lights. My vision is still a little blurry from the treatment. All of this is getting better day by day so that is the next step."

Last year, 51-year-old Roberts was diagnosed with MDS -- or myelodysplastic syndrome -- a disease of the blood and bone marrow that was once known as preleukemia.