/diy/ - Do It Yourself

I think it would be fun to build a hut/shed/workspace kind of building from these type of concrete lego blocks. Should be possible to leave gaps for the windows. Biggest question right now is how to make a roof? Preferrably with some kind of prefab components since I have no building experience at all.
Also, the blocks I found for sale locally are 80x80x160 cm and cost 80 eurodollars. That means I can stack 3 to get to a reasonable height of 2.4m. It would imply you can build, say, a (almost) 5m long and 2.4m high wall for 720 euros. Would you say that is a good price for a load-bearing wall of that size, or is this retardedly expensive?
Lastly, anyone ever seen these used for something other than open-air storage units for sand and shit?