After being roasted by comedians on Saturday night, pop singer Justin Bieber issued an apology to the nation for his past behaviour.

The 21-year-old acknowledged that he has been known more for his run-ins with the law than his music as of late, and vowed that he would be better in the future.

"I've turned a lot of people off in the last few years," Bieber began. "But I know I can still put out good music and turn everything all around.

"There was really no preparing me for this life. I was thrown into this at 12 years old; I didn't know what I was getting myself into. There were moments I am proud of. And there are moments I am disappointed with myself for.

"But the things I have done don't define who I am. I am kind-hearted person who loves people. And through it all, I have lost some of my best qualities. For that, I'm sorry."

In September, the pop star pled guilty to misdemeanor charges of careless driving and resisting arrest in Miami, and he pled no contest to vandalism in July after egging a neighbour's LA home. Accusations of interfering with a flight crew during a Super Bowl trip in January 2014 were dropped, as well as charges that Bieber assaulted a limousine driver in December 2013.

Following his legal troubles, the singer cleaved even closer to his friend and mentor, Hillsong pastor Carl Lentz. He reportedly went on a religious retreat with Lentz in October, and was frequently spotted at the church's New York and Los Angeles locations for worship service and bible study last fall.

Bieber called the Comedy Central roast "a turning point" in his life.

"I am looking forward to being someone you can all be proud of," he explained. "Someone close to me once said, 'It's how you rise from a fall that truly defines you as a man.' I'm excited for that challenge. And I want to say thank you for taking this journey with me."