Robbie - I sold an '84 Schwinn World Sport completely rehab'd and in excellent condition for $160. About market value anywhere I think.
It was completely original. For earlier versions with steel wheels subtract $50.
As a fixed gear, it depends on your market but here it might get
LESS than $20. ( I.e., They simply don't sell modded that way. )
PS- Without a picture of the Ross or at least a model name it would be VERY hard to guess at a value.