Rotors have a bit of the pad material smeared across their surface. That's the only thing that will really hold on to the lubricant. Otherwise, rotors come clean come clean pretty easy -- smooth stainless steel doesn't hold on to much. I'd sand them with fine sandpaper (200-600 range) and then just wipe them off with rubbing alcohol. That will physically remove the silicone from the rotors. Brake cleaner works, but that's pretty aggressive stuff.
If your pads are metallic, you could try heating them. Here you are looking for a chemical change. But silicone resists heat pretty well. Any normal oven won't get hot enough, which is why you can use a silicone mitt to take out your roast chicken. You've got to go over 500 degrees F, with a blowtorch, to break off the organic chain of the compound and leave behind SiO2.
Easier just to replace the pads, like most everyone else said. Then be sure to re-bed your disc brakes by slowing yourself, one brake at a time, from 15 mph to 5 mph or so, about 10 times each wheel.