That does complicate things! I have seen IC socketed ends like that, but not with the Rossin "R", before. They are certainly from the very late '80s at the earliest, but more likely from the '90s. It's possible that this frame is actually a product of Rossin, but also possible that the IC frame bits were purchased (or salvaged from another frame) separately...Be interesting to see pics of any other Rossins from that era that used similar ends and forkcrown.