where can i get those boards with the spikes to prevent birds from landing on my roof?

Answer 1

http://www.taubenabwehr-shop.de/stainless.html

Answer 2

Be careful my friend, you may just get a lot of people sore at you, bird lovers you know.
It's also against the law in most States to harm or injure songbirds and in fact, there's either a heavy fine or jail time to insure no one harms song birds so, I would check with the Department of Natural resources to make sure you can do this.
Just to inform you.