admin answers:

To maintain a secure seat for the roof, remove the fascia, existing shingles and roof sheathing back to the house side of the top plate. Secure the new joist to the top plate, install the new sheathing and install the new shingles. The new joist can be toe nailed to the plate and through nailed to the adjacent existing joist to increase the strength of the joint.
The existing fascia board is not structural, it is a closure piece and installed for aesthetics. Fastening into the end grain of a piece of wood is not recommended, lag screws, etc. Can not come close to developing the strength of the wood member. The 13′ or 14′ span on the new roof will add a significant load to the wall but it should provide adequate support.
Without having a wall around the new addition you should make certain to provide for the potential wind uplift load on the open roof. The support columns, assuming completely open on three sides, should be secured with a strap to the top plate and should be anchored with an anchor bolt to it’s foundation. A high wind into the pocket under the new roof can create a large uplift force on the roof. The support members should be checked for their load capacity on the 13′ or 14′ span. Some supplemental supports or larger than normal members may be required if the roof will be subjected to large roof loadings. Snow load?

What ever you do, do not try to support the ends of the new roof members, by trying to fasten them by end grain fasteners. Doing things the wrong way does not make it correct, no matter how long you have been incorrect.