“Cause I am a champion and you’re gonna hear me roar
Louder, louder than a lion”

Katy Perry – Roar Lyrics on LyricsMode
EXPLANATION
She is saying that she was quiet before and that. She isn't going to be that she is louder than a lion and your gonna hear her she has something to say instead of just listening to him all the time also she is telling everybody that girls shouldn't just allow boys to brush past them and ignore them like they are some some scrap of dirt that they can pick up and discard any time they want.
EXPLANATION
We are all champions and we don't have a right to hold someone else back. It's not okay. We have the right to "burst forth" and show our talents. She wants everyone to take that risk, be a risk taker! I know I can do it, I know you can do it. Taking risks is awesome. Don't let anyone hold you back. Show your inner beauty and talent. Everybody has their talent. She means.
EXPLANATION
She is saying that she is the best of the best and she wont let anyone do better than her because she wants to be the best and better than anyone else.
EXPLANATION
She's tired of being cooped up in the corner all her life she is trying to show the world who she is. She's saying she doesn't want to be bossed around. She wants to stand out. She wants to be herd. She doesn't want to be denyed. She wants to be outstanding she wants to be terrific. She thinks no one appreciates her imputs she wants to be noticed. If she noticed she promises she can make the world shine. So she needs noticed she needs to be appricated and noticed. One day she can be amazing, perfect. She can be a star. Everyone can. You can make the world shine.