Belisario, a right-hander, went 4-8 with eight saves and a 5.56 ERA in 62 appearances with the Chicago White Sox last season. He was 13-8 with a 3.24 ERA over the previous two years with the Los Angeles Dodgers.
Casilla is a .247 career hitter over parts of six seasons with Baltimore and Minnesota. Zarate pitched this winter for Tigres de Aragua of the Venezuelan Winter League.
Tampa Bay also said Monday it had invited minor leaguers Brandon Gomes, Andrew Bellatti , Dylan Floro, Luke Maile, Taylor Motter, Vince Belnome, Boog Powell and Daniel Robertson to big league spring training.