How would you like to be able to pay your rent in flowers?
'Red rose rent' is specified as being a type of "quit-rent," which is not a commonly used term nowadays. It has its roots in feudal Europe, in which a tenant either worked the land or provided military services for his liege lord (either the king or a lesser noble) in lieu of paying rent or taxes on the property he occupied. In essence, the quit-rent took the place of feudal services. The practice continued all the way into colonial America, where the quit-rent was more or less a kind of land tax. In the case of 'red rose rent,' though, it's a merely symbolic gesture, usually because the person creating the rental agreement was being generous for one reason or another. For the princely sum of one red rose every year, the renter continues to have the full use of a specified building or tract of land.
I don't think there are too many modern examples of 'red rose rent' being used anymore, the economy being what it is. But here in Pennsylvania, there are a number of historic locations which still pay homage to the tradition, and one of these is a church in Lebanon County.