The short answer seems to be that Ronda has no assigned IATA code, and RRA isn't in use anyway. That's according to IATA's own directory; third-party sites aren't always reliable.
An airport was in fact proposed for Ronda in the 1980s and never built; the City rejected the license application in 1983. I found two old articles about it from El País: in July 1983 they reported a dispute between the airport's promoter, Prince Alfonso of Hohenlohe-Langenburg, and the Ayuntamiento de Ronda (the city council):
Su promotor, el príncipe Alfonso de Hohenlohe, pretendía sacarlo
adelante con una licencia de obra menor por valor de medio millón de
pesetas, y asegura que para montar el Marbella Club y lanzar el
turismo en la Costa del Sol no le pidieron tantos requisitos. El
alcalde, el socialista Julián de Zulueta, recela de intereses ocultos
tras el proyecto, descarta la tesis de que se trate de un simple
aeródromo deportivo y no está dispuesto a permitir su construcción si
no es con todos los requisitos.
Its promoter, Prince Alfonso of Hohenlohe, claimed he could proceed with a construction license for less than half a million pesetas, and said that building the Marbella Club and promoting tourism in the Costa del Sol hadn't been so demanding. The Socialist mayor, Julián de Zulueta, is suspicious that there may a hidden agenda behind the project, rejects the claim that it will be a small, recreational aerodrome, and is unwilling to allow construction unless all formalities are complied with.
By October the same year, the council had formally rejected the plans:
El Ayuntamiento de Ronda decidió, en pleno extraordinario, denegar
cualquier licencia para la polémica construcción de un aeródromo en
las afueras de la ciudad.
In an extraordinary session, Ronda City Council decided to deny a license for the controversial construction of an aerodrome on the outskirts of the town.
The articles say the runway was intended to be 2,200m by 80m (7,200ft by 262ft) which, if true, certainly seems to be excessive for the light, recreational traffic and gliders that the Prince claimed would use it.
I couldn't find any more recent references to an airport in Ronda.