I got young niggas that's rollin' I got niggas throwin' b's

from Meek Mill – Intro (Dreams and Nightmares) Lyrics on Rap Genius

He knows members of the rollin crip sets ie. rollin 60’s, rollin 100’s, pertaining to the next line saying he has niggas throwing “b’s” which is the hand signal for bloods, he’s trying to say he’s cool with both gangs

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