The press secretary acts as spokesperson to the president and relays information to the American public, and answers questions from the media.

Spokespeople is the plural of spokesperson

The spokesperson's role is to speak for the group.

He became the spokesperson for the Nazi party.

Someone who is taking on a spokesperson role is speaking for a group. If you were in a class where you had to do a report and you volunteered to present the report to the class... you would be taking on a spokesperson role, or acting as the spokesperson.