Are there different breeds of roaches, or can the little one grow to be huge?

I am feeling a little queasy even asking this question, but I was at the Richmond (VA) coliseum recently, and there were 2 of the hugest roaches eating on a crunched up cracker right near my feet...at my seat. I was disgusted and all I could do was pay attention to these mive things. (they were about 3" long, not kidding) Are these a different breed than the little ones I have seen before? Or are they the same...just way bigger? Oh, just the thought makes me want to lift my feet off the ground.