With the exception of Au Ra, ALL of the races in FFXIV are interpretations of races from other games. Hrothgar aren't Ronso any more than Roegadyn are Galka. They are inspired by Ronso, sure, and with the right customization options can look very similar to Ronso, but bottom line, they are their own race.
Viera being so very similar to FFXII's Viera (even keeping the same name!) is the EXCEPTION, not the norm, and very likely the decision to make them exact copies was due to perceived fan demand. They had a lot more flexibility with the Hrothgar, because they were less likely to cause an uproar with every little change they made to the original Ronso design. (There was an uproar, sure, but it's not about how non-Ronso-y the Hrothgar are...)