Parker will fight overseas now, and probably in the United Kingdom for big money and exposure. He said: "It's probably one of the last ones here for a while. I want to thank you all for supporting me in my career so far.
"It's time for us now to go overseas and get some exposure overseas."
Trainer Kevin Barry said: "I told everyone when they wrote Raz off that this was a tough fight, tougher that Hughie Fury.
Barry, who earlier supervised his light heavyweight Umar Salamov's excellent fourth-round knockout victory over Emil Markic, added: "He's a very proud man as you could see today. He was fighting for pride and dignity."
Cojanu said: "This is the moment of truth. I don't know if I deserved that one-point deduction... I saw the fight much, much closer than it was on the score card.
"I taunted him... I gave everything I had."
Cojanu mocked Parker in the first round, shrugging his shoulders and giving a look as if to say "Is that all you've got?". Parker, though, kept his shape, changing his levels with his jab and throwing an excellent combination with nearly 40 seconds of the round to go, backing Cojanu up into a corner and surely gaining his respect.
The second round finished with Cojanu giving Parker a big smile, but earlier the Kiwi connected with a left hook and then with an overhand right which backed up his tall opponent. Parker also missed with a wild overhand right, a sign perhaps of a little frustration.
Both fighters were warned for pushing and holding by referee Mike Ortega in the third round, perhaps Cojanu's best for the fact he connected twice with two-punch combinations, virtually the first time in the fight he took a risk and let his hands go.
The fourth was Parker's best until that point. He backed Cojanu on to the ropes and threw a combination, including a right hand which snapped his opponent's head back. Cojanu then reverted to type, holding Parker around the neck, and he was deducted a point by the referee for his efforts.
Parker continued his dominance in the next round, but there was a mounting desperation from Cojanu, who was beginning to let his right hand go. Parker took a glancing blow with one and missed another. Both were delivered with power if not accuracy.
The holding and hitting continued from Cojanu, who was constantly flat footed in front of Parker. Ortega could have taken another point off him at the start of the sixth but was either unsighted or conned.
The seventh round featured more of the same. Parker connecting with a solid short right hand and Cojanu laughing it off, saying it hit his shoulder.
In the eighth Cojanu pumped his chest after hitting Parker with a couple of right hands, one of which hit him in the back of the head. Parker hit him with a right, left, right combination which had Cojanu beating his chest again.
Parker missed with a right uppercut in the ninth and couldn't budge Cojanu when he connected. Parker's frustration was clear and it was echoed by the crowd.
The 10th round burst into life late. Cojanu, shouting that Joe was running from him, connected with a left hook, but Parker finished with a good flurry of his own; Cojanu hitting him after the bell.
Cojanu might have had claims to that round and he was probably better in the 11th too.
Parker's response was a big round 12, an aggressive flurry at the end which had Cojanu backed onto the ropes and in trouble. Fortunately for him, the bell sounded, but he threw a punch regardless, an act typical of this at times frustrating, awkward but ultimately successful night for Parker.
