The British model-actress was photographed outside the Chateau Marmont with the pricey diamond on her finger, reported TMZ online.
Back in July intimate images of Stewart and Sanders appeared. The "Twilight" actress even confessed to an "indiscretion" with the married filmmaker behind boyfriend Robert Pattinson.
In the wake of the scandal, Ross was seen without her wedding band, fuelling speculation that she and Sanders were no longer together and ever since she has been snapped with a bare ring finger.
However, their relationship appears to be on the mend.
The news comes just days after it was reported that Stewart has rekindled her romance with Pattinson.