It's no longer "unconfirmed." Lawrence Gilliard Jr. (likely best known for his role as D'Angelo Barksdale on The Wire) is indeed joining the season 4 cast of AMC's hit zombie drama series The Walking Dead, in a new series regular role.
Of course the question we all had yesterday was, what role exactly could that be, especially with key black roles already filled, like Chad Coleman (who plays Tyreese, and who's also a former cast member of The Wire) and Danai Gurira as Michonne.
Sonequa Martin-Green (who plays Sasha, although she's not a character that exists in the comic book source material) was promoted to series regulars in the series, which returns in October.
Now we know what role Gilliard is going to play. A character named Bob Stookey.
The local town drunk of Woodbury and a former army medic, who descended into alcoholism before the zombie apocalypse. After the apocalypse, Bob was one of many survivors to join The Governor's settlement in Woodbury. His frequently drunken state worried many in the community, apparently even The Governor himself, as he was encountered by the man outside of his apartment and on the streets. His minor role in the story-line expanded significantly when he became the person responsible for saving The Governor's life. He was called upon by Gabe and Bruce Cooper to save The Governor when Alice and Dr. Stevens, the only town medics, had deserted the town. His summoning was due to Michonne's torture of him, nearly to the point of death. Bob was successful in saving The Governor's life, much to The Governor's own disbelief. After a slow recovery, The Governor personally asked him to watch over his undead daughter until he and The Woodbury Army returned from eliminating The Prison's survivors.
Obviously much has changed in the translation from comic book to TV screen, so a lot of what you read above won't be happening in the TV series, given what's already happened.
Oh, and by the way, in the comics, Stookey is a late 50's to early 60's white man. Clearly the show's producers are taking creative license with the character. However, I'm sure that won't stop certain fans from from crying about the race-switch.