I can't speak for all rotors, but all of the rotors that i have seen over the past 30 years, cannot be taken apart, the parts are not service removable - for a regular television rotor - Channel Master, Radio Shack, RCA etc..

The closest I have come to repairing them was to take a can of PB Blaster and spray the bearing until it freed up and then turn it back and forth until I got as much of the rust out of the rotor bearing as I could.

Most rotor shafts are permanently welded to the armature plate inside of the rotor, but like I said before, if it doesn't have a brake and if it doesn't have a reluctor to tell you where it is pointed - it is a crap shoot every time you use it.

I have a old Channel Master TV Antenna rotor on my one tower that has a Solorcon A99 on the top, a 6 element - Two Meter beam below that and a Six meter dipole below that. But the rotor is nested 10' below the antenna's and the thrust bearing takes all the abuse when the wind blows.
That rotor has to be 40 years old, and it has been on 4 different houses before it ended up on my tower.

You won't find a new rotor with bearing and gears like what is in this rotor anymore. Even when the bearing rusted and froze, all I had to do was spray it with PB Blaster and replace the rubber gasket and it would work as good as new again. The bearing is sealed, I don't know how you could put grease in it. You could put grease around the bearing, but that would only create more problems, not solve them.

There is usually a weep hole in the inspection plate that has to be kept clean so the moisture that accumulates inside of the rotor housing can drain when there is a temperature change.