To encourage or support someone or some group of people with raucous cheering. A noun or pronoun can be used between "roar" and "on." The stadium positively shook as 40,000 fans roared on the home team as they took to the field. We were nervous about playing in front of such a large audience, but the sound of our fans roaring us on filled us with confidence.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.