This idea just crossed my mind and i wonder how practical is this.
As we all know, travelling from one place to another (even within a city or town) can be rather far. For example, from your backpacker to a fast food restaurant which located 1 mile away.
So instead of using your foot to walk, what would you say if we use rollerblade as a mode of transportation when we travel around Europe ( I am not referring to long distance travel ). is this practical?
any tried this before?
Depends on the places you intend to visit. Alot of europe has cobbled streets which would get in your way big style. If your going to travel on trains only then why dont you try pick up a cheap cycle? and just give it away before you leave europe.
i think good luck with the cobblestones.
and even more good luck with the crowds.
i wouldnt recommend rollerblading around cities like amsterdam in anything that doesnt stop easily!
Well, there are a few places where rollerblading is practical way to get around. You just need to be very enthusiastic about rollerblading in order to drag skates around with you all the time in the off-chance that you might be able to use them. Or you need to plan your whole trip around skating routes. The problem with the latter option is that information is very hard to find, as it is published only locally.
IMO a better alternative to rollerblades are folding bikes with touring racks and panniers. (Look at Dahon.) Bikes deal with cobblestones and rough terrain much better, thus there are more options for cyclists than for skaters. A bike can easily handle distances of 40 kms and more - try that with skates.
I agree with everyone, a bike would be a better option. There are too many cobblestoned streets to deal with plus crowds. You'd be ok in bike friendly places I suppose, although I've NEVER seen a single pair of rollerblades anywhere in Europe so maybe you'll stand out 
Oh, and taking them off/on and switching with shoes and lugging those skates on your back whenever you enter and leave a building would have to be tiring. I don't expect rollerblades to be allowed in any buildings and it's not like a bike, which you can leave in a bike rack or chained up somewhere.
Rollerblading would be fine if you were just going to beach resorts as they usually have a nice smooth promenade to skate on if they are well known resorts in spain or france etc, but to travel around towns and cities on them, well I don't think it would be much fun. For example Amsterdam would be pretty much impossible because of all the cobblestones and small pathways. I go to Amsterdam a lot with my friend who is in a wheelchair, and that is quite tough, but I think on rollerblades it would be very hard indeed.
But lots of European cities have events like Friday night rollerblading through the city or parks (for instance Amsterdam, London etc.) so if you don't mind carrying your rollerblades around, there are plenty of opportunities to use them. And if you go to the South of Europe, there are long boulevards to skate on. Coastal cities in Italy and Spain are great places to rollerblade.