A 1946 Paramount Deluxe Dining Car, moved to Rockford, MI along with 3 other diners, to form the "Diner Museum". This never seemed to really get off the ground, and really only this diner (which operates as a real restaurant) and another diner turned into a bar do much of anything. Rosie's was recently featured on the Food Network show "Diners, Drive-Ins and Dives" (with it's ultra annoying host). They make sure you know this, as they plaster it all over the menu.
I made a special trip 15 miles back to here in the morning for breakfast. While not bad, it wasn't anything special either. I could have had the same thing for a buck less only 1/2 mile from my motel. The service was also somewhat slow and neglectful. (And no, it wasn't all that busy either.)
They have a website here with the history of the place.