Here are some suggestions:
Rodney "the Hindenburg" Williams, because he seems to float forever, but when he comes down, he causes explosions. (From the crowd!). Then, the students could chant "Oh, the Humanity", when Rodney dunks on somebody.
Or, how about Rodney "Glaucomys sabrinus" Williams (it's a type of flying squirrel). Sure, it's hard to pronounce, but at least it's unique.
Nicknames like the "Osseo Assassin" or Skywalker, or anything like that is too pedestrian. Frankly, my favorite nickname for Rodney is Rodney "the Black Jewish Jordan" Williams. Williams reminds me a lot of Sam Jacobson, who was of course known as the Jewish Jordan (despite being about as Jewish as Ralph Engelstad). So, I think "the Black Jewish Jordan" would be a great nickname for him.