According to Dictionary of toponymy of G. GASCA QUEIRAZZA, C. MARCADO, G.B. ROMERO, G. PETRACCO SICARDI, A. ROSSEBASTIANO, published in Turin year 1991, the Ropolo last name derives from the name of the villa Roppolo, that is to 31 km of Vercelli.
The name of Villa derives from the germanic Rotpulo, or from the gálico diminutivo Roppulus (of Roppus).

But it is more probable that it derives from piamontés ròpol, diminutivo of ròcol, that means "high place where networks tend to hunt the birds."