In Game of Thrones Season 2 Episode 8 The Prince of Winterfell, Ros is shown to possess a Lannister lion necklace given to her by Tyrion.
Cersei: Varys isn't the only one with who hears whispers. Really, a Lannister lion necklace. You need to hide your secret whores more carefully.
I checked the first episode and Ros is not wearing the necklace when she has her first scene with Tyrion. I do not recall when I first saw her wearing it. When did Tyrion give the necklace to her?
These are the times he could have given the necklace to her:
- In Winterfell on his way to the Wall
- In Winterfell on his way back from the Wall
- In King's Landing, ...
particularly after the incident in Season 2 Episode 4 Garden of Bones where Joffrey made her abuse Daisy.