The first time I passed through the Rohtang pass (a little more than 50 km away from Manali) it was on my way to Leh. We had started at 2 am from Manali and when we reached the Rohtang Pass, an hour or two later, the place was bewitchingly beautiful.
As far as the eye could see, there was snow and silence. A narrow road passed through it and I thought I would like to visit it on its own. It is anyway a very popular tourist spot. I never realized the beauty lied in being there at the off-peak hours!
I passed through the Rohtang Pass again while coming back from Leh. This time it was 11.00 am in the morning and I just could not recognize the place. As far as the eye could see there were vehicles parked all over the place and temporary tents selling food have sprung up everywhere. The Pass was crowded and as we Indians litter like maniacs, the place was dirty beyond recognition. The views in the distance were still as beautiful but I am not sure that I would enjoy it much if it was a stand alone visit.
It also did not help at all that we sat in a traffic jam for hours. As the roads are narrow even a little bit of indiscipline can cause a long traffic jam on the mountain roads. As we were coming for Leh which is a very long and arduous journey with one night break in Keylong, all I wanted to reach Manali early and crash! But we had no such luck, the jam cleared only after a long time. I arrived in Manali completely tired and quite underwhelmed with the Rohtang Pass. I would say the real trips start after you leave Rohtang Pass behind!
PS. The first image near Rohtang Pass is from a trip in 2015. The second is from 2005.