The roof top unit condenser coils are all frozen and covered in ice, what could be the reason for that?

Several. Check a/c filter to make sure it's clean. It could be a leak or an air restriction somewhere.

XenoSapien

This sounds like you have a heat pump, if so then I would venture a guess that the reversing valve is not reversing ,may be bad coil on reversing valve, bad relay for reversing valve, broken wire to reversing valve or thermostat not making the reversing valve wire ("O" or "B") or it may have a bad defrost control. Mike

Are you sure it is the condenser coil? Or is the coil insisde the unit? If so be sure the blower is running, check the filters, and make sure the coil is clean.

It is a heat pump that is freezing and could be inside unit rather than condenser. Have turned off unit and left the fan running. Biggest problem is companion is just out of hospital and it is late and feel helpless.

Are you sure it is the condenser coil? or is the coil insisde the unit? If so be sure the blower is running, check the filters, and make sure the coil is clean.

Not sure if condenser or inside coil. It is on third story and in closet under filter. Companion is just out of hospital and really worried about getting cold. 23 out side tonight. I have turned unit off and left fan on. Is there anything else I can do tonight?
Thanks

If I read your description correctly it sounds like your evap coil is what is freezing up. 23 degrees F? Your heat pump won't be very effective at that low ambient temperature.