Yeah the bands are longer and looped over a roller at the muzzle. The idea is that you get the band pull of say a 100 cm gun on one that is only 75cm smooth power pulled all the way to the muzzle Another benefit is that the pull on the barrel that would normally bend it is now on opposite sides and there is very little barrel flex. So theoretically you can have a thinner barrel. Personally I think the idea of having the same band stretch ratio as a normal gun is wrong on these. I think it is better to reduce the ratio slightly and allow a smoother delivery with the same power rather than just going for more. That's only my thoughts as I haven't used a roller gun.
With regards tracking it the biggest problem will come from the more complex water flow over the extra bands etc. This will be much like having an extra set of bands on an ordinary gun. So it shouldn't be a big disadvantage. A roller gun will be noisier because of those moving rollers but with potentially a faster shaft speed the fish will probably be dead before it hears it so to speak.
With regards tracking it the biggest problem will come from the more complex water flow over the extra bands etc. This will be much like having an extra set of bands on an ordinary gun. So it shouldn't be a big disadvantage. A roller gun will be noisier because of those moving rollers but with potentially a faster shaft speed the fish will probably be dead before it hears it so to speak.