This is what the Wiki say’s

He initially composed music jingles for advertisements, Indian Television channels and music scores in documentaries, among other projects. In 1992, the first time he got chance to enter in film field, through a Malayalam film named Yodha. Its director Sangeeth Sivan who realise Rahman’s talents already. And with this good entry he was approached by film director Mani Ratnam to compose the score and soundtrack for manirathnam Tamil film Roja. The debut led Rahman to receive the Rajat Kamal award for Best Music Director at the National Film Awards, the first time ever by a first-time film composer.

This is what the Wiki say’sHe initially composed music jingles for advertisements, Indian Television channels and music scores in documentaries, among other projects. In 1992, the first time he got chance to enter in film field, through a Malayalam film named Yodha. Its director Sangeeth Sivan who realise Rahman’s talents already. And with this good entry he was approached by film director Mani Ratnam to compose the score and soundtrack for manirathnam Tamil film Roja. The debut led Rahman to receive the Rajat Kamal award for Best Music Director at the National Film Awards, the first time ever by a first-time film composer.

Even i have a doubt on this..i strongly believe Yodha was his first!!..I knew ARR used to work as a technician in Malayalam film industry..i think he first started work on Yodha..though Roja was the first to be released..lemme check for release dates