Root servers sit at the top of DNS. There are root server addresses (A through M), but hundreds of physical servers worldwide use anycast to share these addresses.
Root servers don't know individual domain IPs. They know which servers handle each TLD. Ask a root server about google.com, and it says "ask the .com servers."
Root servers rarely handle queries directly. Caching at lower levels means most DNS resolvers already know where to find TLD servers.