Rosniak appeared as Tony in 1997's Spellbinder: Land of the Dragon Lord, and in the same year voiced the title role in the animated television series The Adventures of Sam.
[1] In 2010, Rosniak was cast in a supporting role in Animal Kingdom and in 2011 was in Underbelly: Razor, playing the part of notorious Australian career criminal, Squizzy Taylor.
[2] In 2018, Rosniak was one of the regular cast members in the comedy series Squinters.
[3] In 2023, Rosniak joined filming for the Nicolas Cage led The Surfer.
[5] On 19 August 2024, Rosniak was named as part of the extended cast for the Australian adaptation of The Office.