I just made a Rosemary-Valencia Saison yesterday. It's sitting in the primary, now. I used one fresh herb package from the grocery store in the last five minutes of the boil, then pulled them out. I used an equal weight of Organic Valencia Zest. I expect the flavor to be HUGE, and I kind of want that, actually.
My wife and I make a tea from fresh rosemary. We use fresh rosemary from the garden, in large handfuls, brought to a boil in a full pot of water, with between half a cup and a cup of sugar. stir in the sugar and let it boil for just a minute, or two, then let it steep and cool. It's great iced on a summer day!
Rosemary is related to mint, and the herbs play well together. If you want to increase the zip in your tea (and I presume in your beer) a small touch of mint works wonders to enhance the pine.
Sage also plays really well with Rosemary in brews and our simple sweet tea. Last year, my most popular beer was a Rosemary-Sage Saison. 1/2 oz of fresh rosemary and 1 oz of fresh Sage, in a medium-brown honey saison. It's the same ratio we use when we make a sweet herb tea from the fresh plants.
Regarding the flower usage: I strongly discourage that in general, except in proven cases from master brewers where the recipe calls for the flowers. When the plant flowers - farmers call this "bolting" - the stalk and leaves get really, really bitter. If anything, at your home garden, clip the flowers right away when you see them forming to discourage your plant from flowering whenever possible, and if you are harvesting stalks and leaves, avoid those stalks that are flowering. I'm sure the flower is lovely, because the plant is throwing so much energy into it, but the rest of the plant will *not* be good. If one does use the flowers, I don't think any other part of the plant should be used.