Brett Rossi I'm with You, Denise ... Give Charlie Hell!!

Hand Brett Rossi some pom-poms, 'cause the chick is full-on cheerleading for Denise Richards in her battle to get Charlie Sheen to cough up more than a million bucks. 

Charlie's ex-fiancee was in Vegas when she talked about the story we broke -- Denise blasting Charlie for allegedly cutting off financial support for their kids, and sending nasty text messages.

Brett famously ripped Charlie after he revealed he has HIV, and she's obviously very happy to see another Sheen ex opening up a can. Check out the clip ... Denise might appreciate the support, but she'd really love it if Brett got her daughter's names right.