The rose garden lies within the confined walls of President Snow's mansion. It serves no purpose in the Games, but it is where he and Seneca Crane consult with each other to discuss the events that shall take place within each Hunger Games, such as new tactics, ideas and above all, the competition and talent with each year's fresh batch of tributes.
The rose garden appears in a short scene where President Snow and Seneca Crane are discussing the games whilst the President is tending to his roses. The garden also appears during Mockingjay where Katniss Everdeen confronts him whilst chained to a chair in the centre of the garden. Even after the Capitol was defeated, he continues to manipulate and control Katniss, especially with the scent of his enhanced roses.
President Snow can be seen often wearing an elegant rose on his suit. The scent is described to be sweet and incredibly overpowering, and this scent has a huge effect on Katniss. Katniss is often found complaining that she continues to smell the lingering scent of the roses that Snow wears, especially where he left a rose on the dresser at Katniss's home in the Victors' Village. She mentions the scent during the meeting in Catching Fire before the announcement of the Quarter Quell, where Snow threatens Katniss that he is not convinced that the star-crossed lovers scheme with Peeta Mellark is real. Katniss thinks she can feel the presence of the President everywhere she goes with the haunting scent of his roses being the main reason.