How are 'road-like passages' between Himalayan mountains formed?
It's a glacier, it this case the Baltoro Glacier in Karakoram, Pakistan. The road-like pattern is formed as the glacier slowly flows towards lower altitude from a nearby ice-cap or accumulation zone. Rocks and dirt is transported both within the ice and on the surface. 

With a closer look, the surface is rarely smooth, but often deep trenches, cravasses, and meltwater channels are formed as the glacier moves. On a human timescale, the glaciers crawl slowly, but from a geological perspective they are fast. 


Closeup of a glacier with crevasses. (By Roylindman at en.wikipedia, CC BY-SA 3.0)

Under the glacier, a U-shaped valley is formed as the glacier erode the bedrock. Depending on the dynamics of the glacier and the erosion, the glacier might also appear clean, without sediment on the surface. 


Large glacier without sediments, but also with a very uneven surface due to the movements of the glacier (Wilkes Land).