The winner will likely challenge for the belt that will be defended by Chris Weidman against Luke Rockhold in the main event.
Welcome back to The Crossfire.
Souza is a former Strikeforce middleweight champion and is on a eight-fight win streak.
Romero, an Olympic silver medalist in freestyle wrestling, finished Lyoto Machida in his last contest.
Jose Aldo and Conor McGregor will unify the UFC featherweight title in the main event.