If your home was built with manufactured roof trusses you should never cut or damage them. If the need for modifications is crucial for renovations or repairs you should consult with a licensed structural engineer. Although you may have a recommendation or design plan in place it could be extremely expensive to make these types of structural changes. It is also very unlikely a building code official would even allow you to modify trusses.
Rule #1 when doing repairs and renovations on your home should be never mess with the structure! Plans are on paper/computer and can be easily changed before major damage is done to your home.
Sometimes it is hard to keep your Sawz-All in its case but that is where it belongs in this situation.