It's not really that big of a big deal. A lot of liberties are taken with how the lions function within the TLK universe already, so how they roar isn't anything more unusual than every other change. Besides, most of the roaring we see in the films are victorious and ceremonial roars, not for communication between pride members. In which case, the more realistic take of it would be closer to this:
https://youtu.be/qApvJEfIDrk?t=23sObviously, they're not gonna do that. It'd look silly. It'd seem as if Simba was have some sort of fit.