Sort of iffy. The Roman Empire expanding into India is basically akin to Nazi Germany expanding into the US. But sure, I'll try it out.
So, let's say the Crisis of the Third Century ends with Rome collapsing, and a successor state in Mesopotamia expands into Persia because reasons. Then we see some sort of
Indo-Sassanid equivalent state emerge as a vassal of this empire, and then eventually this state breaks away and unifies India. This is contrived for sure, and by the time this empire gets into India I'm not too sure if it would even view itself as a Roman successor (IOTL, the Indo-Sassanids went as far as to stamp their coins with Oesho, a sort of proto-Shiva popular among the Kushan they conquered, showing how far they went native), but Indians did know of the existence of the Roman Empire, and surely this empire would too.