so what do you call it when you make a sandwich out of a roll but don't cut it all the way and leave the 'hinge' as it were
Lazy.
But I suppose I wouldn't really call it a sandwich if it's in a roll. I just call it a roll.
At any rate, if you're cutting through it almost all the way, you're still trying for a sandwich.
A hot dog bun isn't always cut all the way through, and generally they are held differently, with the opening to the filling facing up. Whereas the 'openings' on a sandwich face horizontally when you eat it.