Hi my roomster horn just stopped working. I checked the fuse its ok .can anyone tell .e where the horn is located and any other ideas what the problem could be

The horn is located behind the left fog light / fog light grill of the front bumper. 

 

There are quite few reasons for horn to stop functioning. It can be the fuse as you wrote, or the switch behind the air bag on your steering wheel, or the wires may come loose or finally the horn itself died.