Normally a red screen means a kickstart problem. If there was a lot of corrosion on the memory expansion it's not unlikely there is corrosion in other places.
Though, looking at the pictures it seems like the ROM chip isn't seated properly. Might just be an illusion of course.
I would gently lift the ROM out of it's socket so you don't damage anything and then reseat it and push it down properly.
A decent way to lift these kind of chips without the proper tool is using a flathead screwdriver, insert it gently between the chip and the socket and twist the screwdriver. Don't bend, twist so the flathead does the job. Do this on both sides and the chip should come out easily.
