found some ideas to build off of (i plan to do one as well):
recently tasted a beer brewed by Defiant - Saison brewed with rosemary
--so we know its doable, i felt it needed more rosemary however.
i was told to throw in 1 sprig worth of leaves per 10 gal batch @ flame out
personally i would go for more, and steep instead as you would hops... maybe @ 15 and flameout? Get the bittering/flavoring and also some aroma at the end.
try making a "tea" (taking into account ratios) with rosemary leaves (fresh) and play around with various steeping times, etc. You can always do this to add flavor later if after primary fermentation you find it doesnt have that rosemary kick!
http://***********/stories/recipes/article/indices/51-recipe-exchange/1362-rosemary-ipa
rosemary + coffee go together - how bout a coffee and rosemary stout