A roll-up banner has maybe 3 seconds to land its message with someone walking by, so those four things you named are really the whole job. It needs to be clean, with enough white space that the eye isn't fighting clutter and one clear focal point instead of five competing ones. It should be visually appealing, but in service of the message rather than decoration for its own sake. It has to communicate fast, with a hierarchy that reads top-to-bottom or in one glance — headline, supporting line, visual, CTA, nothing more. And it needs consistent branding, using the same color logic, type, and logo treatment as the rest of the collateral so it doesn't feel like an orphan piece.