I noticed some years ago that more impressive-looking roller brakes were available. My bike had a BR-IM50-F. I wanted one such as a BR-IM80-F, but I could find none for sale. None online, none in bike shops. Generally they were not even available on bikes in Denmark or Norway. I had bike shop owners argue with me about whether one would even fit my bike. I had people say it was all the same, no point in switching. I had noticed that http://www.workcycles.com sold lots of them, but they didn't really do small part orders. Then, I actually went to Amsterdam. I even had to go to the workcycles shop twice to get through to a mechanic without too much waiting.
So, now I had a BR-IM80-F in my hands. In my carry-on at the airport even, by accident. That got a raised eyebrow.
Anyway once home, I performed the swap. Possibly the easiest part swap this side of a pedal with greased threads. Take off the wheel, apply a 17mm (I think) deep socket, change the shift cable to a new-style cable (had one laying around), done.
So did it improve braking performance? No. Not in any noticeable way.
Here I have laid out a BR-IM50-F, BR-IM80-F and BR-IM45-F with their business sides exposed. The two newer ones appear to be identical except for the cooling surface, and the older one is just damned dirty, also possibly a little worn.
So hopefully by writing this down in the sight of a search engine, others can be informed. These roller brakes are generally not so useful on hills, and getting a "bigger" one doesn't help. I have another bike which, like the one I just modified, has only the potential to mount hub brakes. On that bike I mounted a Sturmey Archer XL-FD (a 9cm drum brake hub), which fits perfectly, brake arm and all, and its stronger though perhaps a little more temperamental. (Niholas use the 7cm version of that drum brake.) Going the Sturmey Archer route does appear to require building your own wheel though, not a big supply of pre-fab wheels built on drum brake hubs.