No longer in Paris, but I don't recall there being an awful lot... at least that you can visit. You might be able to negotiate access to the roof framing of various of the churches / cathedrales (Notre Dame would be superb to visit), but I don't know if you'll have much success if you don't have contacts... and sadly I don't have the necessary contacts.

If you're around for long enough to jump on a train, visit Rouen. It's about 1hr from Paris and you can wander around a more or less entirely half-timbered city centre. Or visit Beauvais (about the same distance, but I'm not sure if there's a train service... there's definitely a bus to link the airport to Paris). The old Palais (now a museum) has some very pretty roof framing (I have some photos kicking around somewhere), and the Maladrerie has some more. Paris itself was largely rebuilt by Hausmann and is principly stone. The roofs are all Mansart and probably interesting to visit if you can get access to them.