Lantz wasn't nearly as big as Roby. He was a 6-3ish guard. Stewart could really fill it up from outside (again too bad no 3-point line), he could take it to the rim and had great hops.
Actually, another 6-3 type player that Roby makes me think about is Greg Downing. Downing had similiar skills as I recall, but couldn't hold a candle to Isaiah's shot blocking & rim protecting.
All that said, because of all the things Isaiah can do and because of his unrealized potential, he's a one-of-a-kind type of player in NU history, IMHO.
And "IF" he would be