This is strictly about linguistic similarity and not genetic similarity.

On a genetic map, a PCA plot, Romans and Romanians simply don't overlap. Romanians cluster with their Balkan neighbors, (1) on account of massive Slavic migration from around the 7th century AD, and (2) on account of strong historical and genetic evidence to suggest that the Roman colonists sent to Dacia were largely recruited from neighboring Balkan provinces (like Moesia and Pannonia), rather than from the city of Rome.

Genetically, the nearest populations to Ancient Romans are Cypriots and certain other Mediterranean types, including Anatolians. But it's not neat; there's no clear unambiguous descent. A lot can happen in >1000 years!

I still find it somewhat fascinating that the Slavs arrived in Europe during recorded history.