Interesting question, flyeater. I just skimmed the end my A&C MEET FRANKENSTEIN MagicImage Filmbook and to my surprise actually saw that there are a few lines in the description where the monster roars!

When Chick is unstrapping Wilbur from the operating table, the description states: "The Monster begins to roar with incoherent anger. The electrodes at his neck are sizzling and smoking. He rages at the straps that hold him."

Then, two pages later, after Wilbur says, "He thinks I'm Dracula," the line of description reads: "The Monster, seeing Wilbur's face, lets out an angry roar and starts for the boys..."

Funny, I never picture the Strangenstein Monster as a roarer. It would have been great if he gave it some of those intense Karloff "Raaaars!" but I don't think ol' Glenn really had it in him. If he did, the powers that be certainly didn't let him give it a whirl. Unless, I'm misremembering "House of Frankenstein." Was he ever audibly growling in that one?