So, it is not about OSHA rules, but it is the issue of insurance or the lack of insurance. If the installer had good insurance he could do a roof install!!!
In my opinion they are interchangeable forces and both apply. Word on the street is that after Mike White the DirecTV CEO was shown on a TV show with what looked like untrained workers screwing around with ladders the word came down. I saw one episode on YouTube that made me wince; clueless worker on an extension ladder with incorrect angle...next step was the ladder sliding away from the roof. Ladders come with an OSHA warning that falls can hurt! So when some OSHA wonk sees clowns at work they pass the word to insurance companies. Insurance carriers pass the word to their customers. I think the real factor was some unstated cost to train employees or provide safe roof work conditions.
Remember that for years and years both DirecTv and DISH were able to function by buying completed installations from subcontractors. One of the costs they were able to avoid with this policy was Workman's Compensation Insurance. As they begin to transition to employee served installation departments this cost becomes significant to them. Since it is true a worker can die from a fall from a thirty foot ladder or the roof above that level it must have become too hard to assure management that workers would be able to work safely in every case.
All this is just my read on the situation. I have climbed all over structures and trees without injury. There were tasks I declined because they were, in my opinion, too dangerous for me to attempt. Others with different skills and or equipment sometimes went where I would not. I also encountered workers who could not function in climbing situations. Instead of sorting and qualifying climbers from non climbers it must have been cheaper to just limit liability and ban off-ladder work for all residential satellite system installers.
OSHA does not control what companies do. They just fine the beejeebers off companies who have injuries due to unsafe working conditions. Insurance underwriters note the carnage and estimate the costs. It is business owners who are free to attempt operations they can profitably undertake. There must be some amount that will buy insurance for the roof walk.......bet ya......but that would eliminate FREE installations.
There are safe ways to do everything....just not inexpensive ways to do some of them. Insurance is a cost of doing business. The bean counters rule.
Joe
AFTERTHOUGHT: Even if you find someone who will do an off ladder installation you will still have a problem. If DirecTv sticks to this policy you will not be able to get service through Directv. Their employee techs will still not be allowed to leave their ladders. You will incur the same costs people who required a forty foot ladder or a cherry picker to get their dish up. The basic installation is a dish attached to the building (and now within reach of a ladder).