I installed new insert at the roof when the old insert was brittle and falling out. 6+ years of sun made it do that. I use sealant a the very ends and also in each screw hole. I also upgraded to stainless steel screws.
I also replaced all the vinyl trim at the roof edge, and down the front too. I used sealant at the front and rear, but didn't pull all the screws and seal them. Too much like work. ๐