It was previously reported that the new roles will include CIA agents Rex Matheson and Esther Katusi, as well as convicted murderer and paedophile Oswald Jones.
Doctor Who Magazine reports that Esther will be "very much an optimist" and a Christian with "a strong faith in mankind". The character will also fall "head-over-heels in love" with partner Rex.
The "dangerous and clever" Jones will also appear to "regret his evil past" and "is fated to become the centre of terrifying events".
A fourth regular character, Dr. Vera Juaraz, will also be introduced in the new run and will become caught up in the Torchwood team's mission.
Casting for the characters is said to be ongoing.
Torchwood: The New World is expected to air on Starz in the US and on BBC One in the UK next summer.