Does your wireless Powertap work properly when riding on
 

1. A trainer (e.g., Kurt Kinetic Road Machine);
2. Rollers; and /or
3. Rollers with magnetic resistance unit?

Yes to those, dunno about the trainer.

um trainer yes it is a rear hub doing the calculations front wheel does nothing

I assumed he was more worried about electromagnetic interference from the magnetic trainers. Could be wrong though. The amount of wattage being dissipated through a magnetic trainer could cause a large enough magnetic field to interfere with wireless communications. Especially weak ones such as the short distance ones from Powertap to computer. Plus the distance from magnetic field to the powertap is quite small.

really depends on the frequency of magnetic radiation the resistance unit is giving off. I doubt it's the same band, stranger things have happened though.

If my cordless phone rings, it kicks me off my wireless internet.

OHHhhhhhh...I use a leather brake....I don't know the answer on that....

if that were the case, you could run a passive antenna...solid copper wire from the back end area of the hub
to the front of the unit, [length in even multiples of 31.25mm ] it could help