Ok this is very intriguing...saw this squib regarding a book written by a retired yeoman guard at the Tower of London called Mysteries of the Tower of London.  A quote from the book goes as follows:

Roses are delivered to the Tower at least every year sice the early 1960s, sometimes in a basket, other times in a bunch, accompanied by a small card, decorated with red roses & bearing the simple message "Queen Anne Boleyn 1536".  And on the anniversary of her execution, 19 May, they are reverently laid on her grave before the altar & allowed to lie there until withered & then removed.

I've seen rumors about this being set up in some sort of "trust" via Anne's relatives as well.  Wonder who's been doing this for the last 40 years or so?