Is there any difference about how the car rolls whith each of this size?Because i want to buy the 195/50/15 wheels,i already had the 185.55/15 on the car about 2 years ago.

that's a difficult question to answer, and i'm sure there will be someone who gives a better answer than me, but, I would say that the difference would be in the manufacturer and the specific tyre bought, and the stiffness of the side wall rather than the width (the side wall should be the same profile for both sizes).

Stay with the correct 185/55 size. It is the best combination of grip and rolling resistance, also they sit better on your 6J rims. There is no benefit to extra width for these cars, even powerful 2 litre HGT models only has 185 tyres. Also wider (heavier) tyres take more energy to spin up to speed and more braking to slow them down.

Some people say they can save a lot of money buying the wider tyres (I don't know why it should be like this...) but for me this is not a good reason. Shop around and find some good tyres, you will get better performance by buying quality.

I have standard 185/55 15 tyres (mid-range Nexen) on my Brava and they look and feel just perfect.

Also 195 tyres are not listed in your manual as an option so they should be declared to your insurers.