For me, the [thing] I felt [made] The Lion King[...]a really good film was[...]these three pillars; you've got 'Circle of Life,' then you've got the stampede[...]and then you've got Mufasa's ghost[...]so it's like those three moments are birth, death, and rebirth.
In 1978, DeRosa enrolled in the character animation program at Calarts, where he met future Disney animator and colleague Mark Henn. Alongside Henn and many other eager students, DeRosa learned the art of animation. Following his enrollment in Calarts, he participated in his first professional project, a video short called Hoomania, which was made and distributed by Adelphi Productions.
This film was DeRosa's Disney debut, as he was given the opportunity to supervise animation for adult Nala. Although Pocahontas was considered the more important of the two films during production, DeRosa had no preference as to which film he was given a lead.
"We had to, of course, bring in the lions into the studio," remarks DeRosa. "[It] was a very important moment, I think, for all the animators[.] [It was] very informative seeing those gigantic beasts close up. It's a different experience when you are that close to them."
Along with Andreas Deja, he volunteered to pet one of the lions, though the experience left him with great respect for the size and power of the animals.