Here are a few suggestions. Others will probably add to the list.

* You said you asked the manager to check. I assume you mean the Managing Agent? What about board members? Have they been approached about this?

* Do you know if other shareholders are aware of the situation and how they feel about it? If your building is not too large you might try organizing the shareholders to take some action as a group.

* Do you know how long the brown spot has been visible? If it didn't just appear but has been there for months you should call 311 and ask them how to report a possible mold situation.

These are things you can do which have a low impact. Ultimately it's your board who are responsible for the condition and wellbeing of the building. If they're receptive to your notifications they should take over.

If they're hostile to you, tight with the managing agent, haven't raised maintenance in years, they're probably not going to start now. You should run for the board, or better, put together a slate of candidates to replace the entire board. Sometimes the mere threat of opposition or replacement can have a wonderfully motivating effect.

Regardless of what you do, it's going to cost money. Be prepared for an assessment to cover the cost of roof replacement.

Good luck!