Resuming everyday activities (work, school, partying, etc) after engaging in anal sex, without cleaning yourself up afterward.....so you're rolling around wearing trace amounts of fecal matter, semen, butt juice, and blood on your skin.
Applies to any manner of anal-oriented sexplay....anal intercourse, ass licking, fisting, rimming, etc. If you leave without cleaning yourself up..... you're rolling dirty.
*** Can also be applied after having sex with a woman who's on her period.
Dude, I was balls deep in my girl's ass this morning....but it made me late for work, and I didn't have time for a shower, so I'm rolling dirty today.