I'm never a fan of any building allowing residents in any shape or form to have their own installations on the roof. The reasoning goes beyond the hazards of having anyone on the roof, but also each hole that is drilled into the facade of the building is a leak just waiting to happen. If it isn't properly flashed and waterproofed you are just inviting the water to come on in. Also, these dishes can tend to be an eyesore and the Prop Lease probably prohibits the installations anyway.

There are two ways that you can go about this, in my opinion. If the problem is related to satellite dishes, you can send everyone a note clarifying the Board's position on this and request removal within a specific time frame. If they don't take the dishes down themselves, you can certainly do so after that time frame has come and gone. There will now be holes in the facade from where the screws were in place, so you're going to either have the building staff, or an outside company come in to patch things up to ensure that there is no water infiltration from that point on.

If there are a lot of people who have their own dishes, the building can look into getting a Master Dish that would serve up satellite to anyone in the building who wants it. This could be costly as the initial installation and wiring in the building will be expensive. The upside to this is that you can do it once and have only one penetration in the facade of the building and it will be regulated by the Cooperative.

If you do end up leaving the dishes, I would make sure that you do the work now to patch up the areas around the insertion points to alleviate the future need for waterproofing repair and possible insurance claims. Perhaps you can set up an inspection process and bill those Shareholders for the cost of maintaning and repairing those insertion points that will cause issues.

Not to mention that you want the dishes to be installed correctly, god forbid one flies off your building and injures/kills someone.

Your current house rules may state something similar relating to hanging of radio or TV aerials from windows or making use of the fire escapes for purposes of placing objects:
Windows.
No radio or television aerial shall be attached to or hung from the exterior of the building. The building is wired for both a TV antenna (located on the roof) and cable TV, which can be hooked up inside each apartment at the Shareholder's expense.

Public Areas.
9. No article should be placed in the halls, on the stairway landings or fire escapes.

The legality of denying permission to residents who wish to install such devices including TV dishes may be founded in the following documents that are available through the Internet. They will help you understand the Board’s rights to decline such requests:
http://www.fcc.gov/cgb/cosumerfacts/consumerdish.html
http://www.fcc.gov/mb/facts/otard.html