The NRL star's ongoing saga was finally put to bed on Monday, the 22-year old officially departing the Sydney Roosters and signing with bitter rivals Souths.

It's understood the dual premiership winner has penned a deal for $600,000 this year and $800,000 for 2021, should the Rabbitohs exercise an option to renew his contract.

While a new Roosters deal, reportedly worth $800,000 a year and a four-year offer of $3.8 million with the Wests Tigers fell over, Mitchell insisted it was never about money.

"The way they (Souths) treat their families is the biggest thing I looked at," said Mitchell, who was flanked by his father Matt and received advice from fellow indigenous players at the club such as Cody Walker.

"I didn't want to rush anything. I love the Roosters but I didn't want to make a decision I'd regret.

He admitted that he "probably would've regretted" signing for the Tigers, too.

"And I understand where the money was at, but it's's not all about the money everyone made it out to be," he said.

There was plenty of speculation about where Mitchell would fit in at Souths, but he made it clear he saw himself as a fullback - and was supported on that by coach Wayne Bennett.

"I have always come up as a fullback - I was never a centre. The potential to play fullback again is exciting and ... I'm excited to see where I can take my footy now.

Asked if he saw Mitchell as a long-term Rabbitohs fullback, Bennett simply offered: "I do".

Of his mental health, after months of interest in him - on and off the field, as well as attacks on social media - Mitchell said he was finally in a good space.

"Mentally, I have dealt with it pretty well at my age. I was going through a stage where everyone was just speculating and that's all it was," he said.

"Just with family, I think it hit them harder than most. My mum was always in tears because of the stories that were coming out."

Souths general manager of football Shane Richardson was thrilled to land Mitchell.

"Latrell is a sublime talent and, with the guidance of our coaching staff, senior players and mentors, we think Latrell can go to another level in the red and green," Richardson said.

"He has the ability to be one of the best players in the world and, from our discussions with him, he understands that it's going to take a lot of hard work and effort for him to be at his best consistently and to reach his full potential."

In 96 NRL games for the Roosters, since his 2016 round-one debut, Mitchell has scored 65 tries.

He has played four Tests for Australia and four State of Origin games for NSW.

Australian Associated Press