Originally from Tuam, County Galway, Rossa is a new, exciting original voice. He's just completed a script for Big Finish's Dr Who. His TV original scripts include Amniyat, currently optioned by LA Productions (MI6 manipulate an NGO doctor to become their go-between in secret talks with terrorists in Somalia); His screenplay based on his experiences in Afghanistan, Checkpoint 54 has been optioned by a BAFTA Award-winning director. He has written episodes of the forthcoming series Killing the Cure and the pilot episode for E.L.E. Rossa's screenplay for One Christmas Night in a Toy Store, is the 3rd in a series of films due to be released in Spring 2021.

Rossa specialises in police procedurals and spy thrillers. Contrapasso (a Russian spy is ordered to poison a defector in London, but uses the poison on his cheating wife); Stakeknife based on a true story (the IRA's internal security chief is revealed as a British spy). He also co-wrote The Circuit, looking on the encroachment of private security into matters normally handled by the police.

Rossa emigrated with his family from Ireland to the UK when he was a child. He spent 10 years in British military intelligence and was awarded an MBE for his services in 2018. He also received a Superintendent's Commendation during the 2 years he spent subsequently in Metropolitan Police Counter Terrorism.