Acosta's manager Charles Garner has denied the recent speculation surrounding the pair, which began when the model was seen wearing a ring.
"The story is that the proposal is false," Garner told MTV. "Miss Acosta is still very much single. She was in LA filming the Chris Brown video with several other models.
"Soulja Boy was in LA. He's been friends with Rosa for a while and asked if she and the other girls wanted to go to dinner.
"The ring she has on her finger is a ring that was given to her by her mother about three or four years ago and it was not given to her by Soulja Boy. The picture that everyone has up is a harmless picture where he's kissing her on the cheek.
"And there's about four other pictures where you see him at the table with her and the other models and he's hugging everybody."
A spokesperson for Soulja Boy also denied the rumours.