I know I talk strangely. The most effective line I've ever used to avoid roof mounting dishes, I'll share here now.
"I cannot promise if you put the dishes on the roof it will leak. I CAN DEFINITELY promise if they're on poles, your roof will not leak." I also have a release of liability prepared for them to read that I will require them to sign if they insist on a roof mount.
What if they don't have the money and can't get it? Then they don't have the money to pay their DTV or WB or DNS bill either do they?
Peace y'all,
Rick