Consider a model aircraft that is tied to fly along a taut wire. It can roll but it cannot slip. Will dihedral tend to restore it to wings level, if disturbed in bank? For answer, consider that for every force that you note on the more horizontal wing, there will be an exactly equal force, providing an exactly equal rolling moment, on the other wing.
Yes, I see what you're saying, Oktas, although in your illustration, the wire is supporting the aircraft; taking the place of the lift. When the wings have to provide the lift as well, the imbalance of lift, (i.e the difference in the vertical component of the lift vectors), will surely provide a restoring force to roll the aircraft level? Your wire will prevent the high wing dropping due to having less vertical lift component than the more level wing, but in the real world the high wing would drop. I will have to get my head around this.