Thank you for the response, Modern Algebra (I love your scripts, btw)!
I had considered Namcor's before, but what made Rocklee's so attractive was the ability to have the characters "cry out" when they're struck. Most of the effects of Namcor's I was able to pull off with common events in battle and stringing the battle cries to animations, but getting the characters to cry out when hit has been a bit of a problem. I tried setting the sound effect to one of my battlers in Melody (I'm using the style that uses animations to make the battlers), but Melody has this weird quirk of making the sound effect echo, which sounds sort of weird.
I thought that maybe I could do it using common events by setting the HP of the character to a variable (thus triggering the sound effect when the HP decreases), but I haven't had a lot of success in making that work.
As for swapping Rocklee's script around--I tried placing it in several places in my script list (above BEM, under, ect), but the problem seems to constantly be that undefined method.
Would it be possible for me to write an extra method into my custom battle system to define what it's having trouble with, or am I on the wrong track?