We are installing a router to access the internet and ASA firewall to protect the internal network. Are access list required in the above case, how would it be used, what would the access list(s) protect? The servers would have private IP addresses. The firewall's main function would be to open ports and close ports for hosts accessing the internet, PAT functions, creating and breaking down VPNs.
Not sure i understand your question, are you referring to access-lists on the ASA or on the router?
The ASA would definitely require permission on either the inbound or outbound access-list depending on your requirement
There is no need for any access-lists on the routers though some are generally configured on the perimeter router but only as security measure and not for any specific access