The UFC record-breaker is at 18 years old, and he's a young man.
The bantamweight became the youngest fighter in UFC history when he joined in September.
At UFC 282 in Las Vegas, Nevada, next week, the American will become the youngest competitor on a main card.
America'sRosas Jr wants to be the youngest UFC champion in history.
At the age of 23, Jon Jones defeated Mauricio Rua to win the light-weight title.
"I'm going to be champion when I'm in my 20s or 21s," said Rosas Jr.
If I were to fight the champion tomorrow, I would finish him.
California's Rosas Jr., who has won all six of his professional fights, was signed by the UFC after his performance in the Contender Series, where he beat Mando Gutierrez by unanimous decision.
White runs The Contender Series but fighters who impress on the show often end up with contracts with the UFC.
The previous record was held by Dan Lauzon, who was 18 when he joined.
With career-changing opportunities on the line,Rosas Jr does not feel any pressure.
I feel free when I'm inside the cage. He said that everything is gone.
I am excited to make my UFC debut and I am having fun with it.
He wanted to be a mixed martial artist since he was four years old.
The moment that convinced him of his future was when he watched his father fight in New Mexico in front of a large crowd.
He moved to California at the age of 12 because he outgrew the gym in New Mexico where he trained.
The most challenging time of his life was when he moved.
He said that he and his family had to live in one small apartment because of the high cost of living.
We got an apartment with more room and then two rooms and then more.
Rosas Jr has had trouble integrating his training with his school commitments.
He said that when he was in New Mexico, he would sleep in the car on the way back from training.
I had to do it somewhere since I wasn't home. I used to do my homework in class in California.
Despite earning a UFC contract, his mother wants him to finish high school.
I haven't been to school in a while, but I'm trying to figure that out.
Tony Ferguson isRosas Jr's favourite MMA fighter.
He is not the same as everyone else. It's funny to me that he doesn't try to be like someone else because of his style.
I like his style of fighting and how he mixes it up.
Despite his admiration for Ferguson,Rosas Jr doesn't want to follow in his footsteps.
He wants to be different but he likes how he is.
Sometimes I don't know what to think. I don't know how I did some moves in my movie.