All C-41 developers are restricted to one temperature. The only difference is that Rollei lies to the customers
. BTW, Tetenal also gives some time-temperature compensations. Kodak and Fuji expect that you develop in standard conditions because there is not a single reason not to.
Of course you can vary the processing conditions but it will cause some color crossover. It is a compromise, or an intentional choice you can make, but it definitely is a processing fault. The results may be good enough, or even near perfect, but that's not the point. The point is, it is because this PROCESS developed by KODAK is flexible. Not because those Rollei chemicals are flexible.
But, I cannot see why someone would like to use other than the correct temperature. It is extremely easy to process correctly at 37,8 deg C. You can vary a bit without large effects, but why bother, as you need a water bath anyway. Room temp development causes significant changes in result. And the development time is so long (keep agitating every 15 seconds, yes!) it's so much easier just to temper the chems and process correctly in less time.
Con artist companies can achieve a higher market value with no real achievements, hindering other manufacturers that play fair. The end result is that we lose possibilities.
This is not just speculation; it has happened before. Let me tell you a story as an example! Disclaimer: please consider this story as fiction, as every detail is not strongly verified but based on my own observations.
Tetenal managed to achieve a very steady business model partly by false marketing; they simply produced inferior, even faulty products but marketed them using strong claims for their superiority. Their RA-4 kit is a perfect example. In marketing, it was revolutionary; easy to mix, especially suitable for hobbyists. In practice, it was harder to mix than competitors and produced horrible results and had a minimal self life, and was more expensive. But, many hobbyists who bought this as their first touch in color printing, just didn't know about anything better. It took more than a year to me, too, to figure out where the problem was!
"Suitable for hobbyist", implicitly claiming that the time-tested products from Kodak and Fuji aren't suitable for hobbyists which isn't true, their products soon became the only available color processing chemicals in many countries. And in the rest, Tetenal was the easiest to buy. So, what they have, is a false marketing that their products are SUPERIOR when in reality they are INFERIOR, just for the reasons they state for superiority such as revolutionary "blix", "monoconcentrate" etc!
And for those hobbyists thinking that randomly varying yellow, muddy highlights and muted, dark colors are normal features in "home color printing", there never was anything wrong with Tetenal RA-4 kit. "monoconcentrate" was still a great marketing claim. Hence, some other small manufacturers copied this idea. The concept had failed technically, but not from a marketing viewpoint.
Now we are at a point it's very easy to buy Tetenal and Rollei everywhere, but the other brands such as "Kodak" and "Fuji" are very hard to come by. Luckily, AG Photographic sells the Fujihunt C-41 and E6 chemicals in Europe now.
] (also found a shop with 1L kit). I was going to go with it, but after reading and searching, found other color dev kits. 
), longer shelf life, various volumes kits (thinking of developing 5 rolls at a time). 
