Nick Cannon -- I Swear I'm Not Creeping with Amber Rose, And Here's Why ...

Just because freshly single Nick Cannon spends a night with smoking hot (and freshly single) Amber Rose at an amusement park ... does NOT mean they're banging -- it just looks like it.

But Nick broke it down for us last night on his way out of a sushi joint in the Valley -- explaining why the video TMZ got of Amber and Nick on a roller coaster Friday night ... is proof they're absolutely nothing more than friends.

He makes a solid point ... unless he's using reverse psychology. Nick does cop to getting into bed with someone -- Robin Leach.