hope for the best expect the worst
Just a laceration, and he walked into the locker room with an ice pack on it, which means it probably didn't need stitches, so its not that deep or long. The knee area is not that vascular, so no serious swelling is imminent. Couple days of rest, without movement so that the dermis can reform its natural alignment.
It's basically like when Eli took that laceration to the face a couple years ago in preseason against the Jets, except less extreme because it wasn't the head. Rolle will be fine with our extra days off...