Seriously, shouldn't Carlton Cole be an easy pick? Speed and Power, good finishing touch, Assists as well as any forward in BPL. God forbid something should happen to Rooney, but who better to fill his role?
Rooney, Defoe, CCole, Bent, and Crouch.
As far as styles, Defoe and Bent are speedsters and Rooney and Cole bring brute strength. Crouch brings something extra with his height and that could make all the difference in a tight game. I'd want to bring all five, but if I must sacrifice one it would be Bent or Crouch. Cole is essential protection for an injury/suspension to Rooney.