Darling, I've smoked both by the tens of thousands and been making both joints and roll-ups since before most of the posters on here were born. If you think a joint looks like a roll up, you must have only seen very bad roll-ups or very bad joints.
I have to concur that I have never seen a rolly that looked like a joint (I made a 10 skinner once, never seen a roll-up look like that :D )