Well, there are a number of "Security" areas of a mojoPortal site: Site settings, page settings, feature settings. I took a quick look through those security areas on my site, and didn't see any called "Site Edit Roles." The descriptions for role settings are all pretty detailed, like "Roles that can edit content and style templates", "Roles that can edit this page", etc. Does your site run with a localization other than en-US? If so, it could be an issue with your resource file's descriptions not being descriptive enough. You can take a look at the equivalent settings on demo.mojoportal.com to diagnose if that's the case.
If what you're seeing has the same description as demo.mojoportal.com, which setting in particular are you looking at? Can you provide a full navigation path?