He's the perfect drummer for the band, no one does that seamless transition from beats to drums like him.
Being a good musician doesn't mean thst you have to be a prodigy, Genne Simmons said that he doesn't remember any Fleas basslines, he prefers memorable parts in music and thats what Rob did.
His style is so unique and he's like the Chester of drums he can play any genre, any style and he always did it perfect.
You guys already mentioned my favorite but the perfect example of how Rob took the songs to the next level its More The Victim holy fuck his drumming made the song so badass.