If he was of Portuguese descent, would he have (mis) spelt his surname (Rosario, I'm guessing) as Derozio? Goa, because of its earlier encounter with European rule, had already had some stirrings in protest here (Pintos, &c).
It is possible that Derozio's mum was Bengali, as the Portuguese were settled there too. If this was the case, the records would have been known, and we would have perhaps not been given the chance to forget it :-) But, in finding out his ancestry, the track runs surprisingly cold!
Regards, FN