How is it called?

Beyond "roadblocks and obstacles," which I typically ascribe to an urban setting, you can also use "terrain" or "landscape," or even "landscape features." I suppose it depends on the feeling you're going for.

It appears the word you want is "obstruction" which can imply blocking movement or sight.

The military uses the term "cover" with a similar meaning for tactical situations, and further differentiates between "hard cover" and "soft cover."

"Hard" cover blocks sight and bullets, such as a brick wall, earthen berm, or large vehicle.

"Soft" cover blocks sight but not bullets, such as leaves, smoke, or tall grass.

yay english. the hardest language in the world!
i am in awe of anyone who wants to learn it as a second language.
all of the options given so far are both correct and wrong depending on the context, location, what its made of, how it got there, if it can be moved and lots of other things.
luckily most native english speakers are bad at english.generally speaking if it sounds right in context, most people will think its right.

debrisor dé·bris[duh-bree, dey-bree or, esp. British, deb-ree]

noun
1. the remains of anything broken down or destroyed; ruins; rubble:
the debris of buildings after an air raid.

2.Geology . an accumulation of loose fragments of rock.

For definition 1. In War ish type games. Debris is usually not an impediment to movement, If the word is used at all. BUT Rubble is often used and it is an impediment to movement of VEHICLES. as the definition states Bombing usually creates rubble, but demolitions and artillery often can too.

For Definition 2. The word used to describe that terrain feature is "ROUGH"