Which Poco C++ PEM file to use?

When creating an application that uses Poco's HTTPSClient, which PEM file should I use -- "any.pem" or "rootcert.pem"? The sample app uses both, but my app is not based on the Poco "Application" class and my app is just consuming APIs from an HTTPS server (i.e. doesn't need private keys).

The server I'm connecting to has a certificate from a "valid authority" and is a wildcard cert (*.company.com).

Thanks for your help.