Roof overrun?? surrounded by business? Once a week, our roof starts leaking. Not too discouraging then it...

Once a week, our roof starts leaking. Not too discouraging then it stops. Is this a costly A/C entry to fix? Is it the overflow on the a/c? Tonight it happened when we turned the A/C temp up from 74 degree to 85 degrees (20 minutes afterwards). Help!!
Whats the cheapest method to build an inground...
Answers:    check your drain hole on a/c, also it may only just need cleaned, and by that i plan take cover stale and hose it down.