Lawyers for the 36-year-old said he was acting in self defence after he was assaulted by Joshua Sutter at their home in LA.
Prosecutors have decided not to file charges, instead asking detectives to carry on investigating.
Speaking three days after his arrest, the actor said he was “very sorry”.
He added: “I am very happy to be out of jail and my heart goes out to the Sutter family”.
Medina said he and a female friend locked themselves in his bedroom after a row with Sutter.
He claimed his flatmate kicked the door open, at which point he grabbed the sword to protect himself.
His lawyer, Allen Bell said: “There simply aren’t facts here for a crime. It is a self defence case.
“You have an individual here who was the victim of a beating in the kitchen area before he went to the bedroom and locked the door to secure himself from any continuing violence.
“He kicked the door in to continue the aggression”, he continued.
Medina was arrested after calling emergency services.
Joshua Sutter, who was also 36, was pronounced dead in hospital.
Ricardo Medina played the Red Ranger on Power Rangers Wild Force in 2002 and later played Deker on Power Rangers Samurai.