All 1996 Roadmasters were "collector's edition" irrespective if they were Limited or not. You either have a base model or a Limited. Limited in 1996 got you: Variable steering the dampener, power seat recliners, split frame design seats, and the Limited Prestige package offered options that the base model did not: Twilight Sentinel, Cornering lamps, memory seats and heated seats and power trunk pulldown. Limited also offered a slew of standard features only available in the base model as options.
This list holds true for 1995 as well. As for 1994 and back, the list of options and standard items were a bit less, such as heated and memory seats were not offered in any model. Also 1995 and 1996 was the only years you could get a Limited wagon. But the wagon's Prestige package offered more than the base sedan in many areas.
You could get leather or cloth in either base or Limited models. The most obvious difference between base and Limited is the seat upholstery pattern (base the same from 1991-1996, Limited same from 1992-1994 and then went all orthopedic for 1995-1996). And functionally the seats are the big difference between base and limited as well, with split frame being the feature unique to the Limited, much like the difference between 1993-1996 Fleetwood base vs Brougham, although Cadillac offered more standard features over Roadmaster in base and upscale.
My favorite seats are the 1992-1994 Limited seats. The 1995-1996 Limited seats that went orthopedic aren't so great. But the memory and heated features are nice. And in all Limited the split frame feature offered better adjustment over the base single frame design.
I said all that to say "collector's edition" is NOTHING special. It just signified this was the last model year for the Roadmaster.