Decks, Patios, Porches and Docks - Filling gaps between roof and frame on porch

I have a house with a screened porch--wood frame with a tin roof. There is about a 2" gap between the frame and roof of the porch which previous owners filled with, what looks like, insulation. It's about the consistency of old plaster and crumbling. Birds have recently poke much of this insulation out and are now inhabiting the porch. Can anyone tell me what would be good way to repair this so that the gap is closed? I am a beginner homeowner with beginner skills, so easy, low-tech (but durable and attractive) solutions will be greatfully received.

Thanks.

This tin roofing -- is that the corragated tin? If so, simply by the wood closures that fit under it and support it. (They should have been used when the roof was installed.) If that's what you are dealing with, 2" is an awfully tall gap. You may need to put a fill under the closures