McBride will sing her Grammy-nominated song "I'm Gonna Love You Through It" during Thursday's show.
Roberts announced earlier this week that Friday will be her last day before taking an extended medical leave to treat MDS, a rare blood and bone marrow disease once known as preleukemia. Roberts, also a breast cancer survivor, will undergo a bone marrow transplant from her sister.
She appeared in McBride's video for "I'm Gonna Love You Through It" last year along with cancer survivors and Hoda Kotb, Katie Couric and Sheryl Crow.
According to a news release, McBride will announce a new partnership to help raise breast cancer awareness.
The Associated Press contributed to this report.