Cardiff will allow long-serving Kevin McNaughton to leave this summer along with Danny Gabbidon and Nicky Maynard.
Highly-rated Atletico Madrid midfielder Saul Niguez has signed a new five-year contract.
The 20-year-old joined Roma's Serie A rivals Chievo on an 18-month loan deal from Boca Juniors in January but only made one league appearance for the Veronese club.
A statement published on Roma's official website revealed the capital club possess an option to sign the attacking midfielder from Boca permanently at the end of the forthcoming 2014-15 campaign.
Roma, who finished second in Serie A last season, have already strengthened with the additions of English left-back Ashley Cole, 22million-euro forward Juan Iturbe and Turkish midfielder Salih Ucan.