He left UConn because they wanted him to play the 4 and he didn't want to (and amongst some issues with Calhoun); UNLV ended up playing him at the 4 anyway. He was leading the nation in rebounding for a while, not sure if he finished #1 though.
And to the original post, yes Grant goes ahead of him. Roscoe Smith declaring will have 0 impact on Grant's decision.