In my experience rollerbrakes are very weak comparing with drum brakes. Is it normal that they have a much larger stopping distance than other brakes or is it just my own bicycle?
In my experience roller brakes can be set up to lock up a front wheel, but it takes more lever force to do that than most other brakes. Many riders consider that a useful feature, but it's disconcerting if you're used to other types, which generally fall into the "lots of force and it still doesn't work" or "a bit too much force will lock the wheel"... roller brakes feel like the former but are actually the latter.
But most bike shops don't do that, and Shimano ship them from the factory requiring a very large force to lock the wheel. It's possible to adjust the brakes to require less force, if you find a bike shop that's confident working on those exact brakes. It is likely to require some asking around on your part to find that shop (realistically, the one mechanic who likes these brakes).
I'm a fairly strong guy with good grip strength and it feels as though I'm more likely to break the lever than lock up the front wheel. In reality though, actually testing this is hard because I had to sprint up to speed, then grab the brake lever as hard as I could, squeezing quickly before the bike stopped, to get the front wheel to lock.
I think that's actually a useful way for a brake to work - it's very hard to lock the front wheel even in a panic stop, because the bike normally comes to a halt before the wheel locks up. The problem is that not everyone has "big strong man" grip strength, so may find that the brake just doesn't work for them.
(full disclosure: I had one of these brakes on the rear wheel and did not like it. I wouldn't have one again if I could avoid it)
It may depend on the bike and the kind of riding, but I am happy with my roller brakes.
I have them on several bikes, but all these bikes are sturdy build (say quite heavy) and I do not go fast and mostly on level grounds as hills are rare where I cycle.
I like roller breaks better than rim brakes, of which I have said not to want them again if I can avoid them.
In my limited experience roller brakes act as good as drum brakes and better than (most) rim brakes in wet weather. They are not influenced by the weather and always react as expected.