Occasionally, it can be difficult to separate the rotor from the hub. If you use a 1/2" "Connector" bolt and a mating bolt, place the bolt between the hub and the rotor, unscrew the bolt against the hub and the two pieces will separate without much effort. Using three of these setups makes it pretty much painless.
Also, if you can't get the bolts holding the rotor/hub together, turn one of your wheels outside down, place the hub into the bolt holes, you can now loosen the rotor retaining bolts so you can separate the two!
While the hub nut wrench was mentioned, a snap-ring plier was not. You'll need an external snap ring plier.
While you're in there, you may as well replace the bearings and hub seals.
Peace,
PT