I'd love to get a lighting effect for the rooftops of a map I'm making. Is there some way to apply a gradient to an object with a pattern fill? Or perhaps it could be done with a HSL Color Effect?

Tom

One simple way is to create a duplicate of the object you want highlighted, and change the duplicate's fill to a gradient going from slightly transparent white to fully transparent. The duplicate sitting directly over the original gives the highlight effect.

Grouping the two will also make subsequent shape-related operations like sizing or skewing work on both, maintaining the illusion.