Hmmmm...you could buy a bead-roller from Harbor Freight for about $100 on sale. The easier solution is to get someone to cut out that section from a donor car. I have no idea how much that would cost, but it shouldn't be that much. I have an idea of where you could get one if you can't find one locally.
I have a bit of rot there, too, due to a broken rear window. Fortunately, it's not bad enough for me to have to replace the whole section.