Roberts wrote the post reflecting on a year ago when she reached the 100-day milestone following a bone marrow transplant.
The post was the first time the TV news anchor has publicly acknowledged her 10-year, same-sex relationship with longtime girlfriend Amber Laign, a massage therapist from the San Francisco Bay Area.
"I am grateful for my entire family, my long time girlfriend, Amber, and friends as we prepare to celebrate a glorious new year together," Roberts said.
Sunday's post thanked everyone who helped her through her recovery.
Roberts' post was confirmed by ABC News spokeswoman Heather Riley.
In the past, Roberts has been open with her family, friends, and co-workers about her sexuality.
After posting her message on Facebook, several celebrities congratulated her on coming out.
"Good morning, America! Congratulations, @RobinRoberts," said talkshow host Ellen DeGeneres via Twitter.
"Sending good thoughts to Robin Roberts. #LoveIsLove," said hip hop mogul Russell Simmons via Twitter.
First Lady Michelle Obama also congratulated Roberts on Twitter Monday.
"@RobinRoberts I am so happy for you and Amber! You continue to make us all proud. -mo" said Obama via Twitter.
In May, Grand Central Publishing announced Roberts, one of the most popular figures in morning TV news, will write a memoir about her battle with MDS and the life lessons she continues to gather following her return to "GMA" last February.