If the Roach Returns...
 

Will the roach talk if it comes back? I think it will ce back at least once by virtue of having a toy.

Unless it's an intelligent being, I doubt it. He's kinda like Justin and Parasite Wasp that doesn't speak the human language or doesn't speak at all.

The turtles have Splinter to teach them. Leatherhead got Kraang experimentation. Dogpound/Fishface/Snakeweed/Spider Bytez/Rat King were humans.

There's only The Pulverizer left. He's not that... intelligent; he might not speak at all in his mutant form.

I think Pulverizer might actually be MORE intelligent now. His inability to speak is a result of the Mutagen being instable and unable to therefore create life forms that necessarily make anatomical sense. The roach probably won't be able to speak because he's more menacing that way.