Yeah, technology just isn't there yet for the surface area of the roof or cargo cover of a pickup truck to get enough electrons to give you enough miles of range to make things worthwhile. Like look at most solar panels. I have 23 optimally oriented panels that are each 67 inches x 40 inches on my house. Each one only generates like 1.3 kWh per day on average over a full year.
And that's sitting there on an unmovable roof with no shade. As people have pointed out your truck is going to be parked who knows where pointing in whatever azimuth your parking space happens to face. And you could have shading from trees and buildings. If your truck is in motion, the solar roof of the truck it's unlikely to be able to charge the truck on the go. A Ford F150 lightning uses 0.5 kWh per mile. So you'd likely get less than 2 miles a day for an even heavier Silverado EV from a "truck solar thing" each day... even assuming the most optimal of conditions where the truck sat stationary while the sun was up.
You're better off investing in a 12 panel array to generate say 5,000 kWh. This will get you about 10,000 miles of travel assuming 0.5 kWh (500 watt hours) per mile and absolutely zero conversion losses*. Some states give net metering credits; or you can do what has been discussed in other threads and literally have the electrons coming off your solar array get shoved directly into your truck.
* Note, solar panels are DC, but the energy needs to be converted to AC; then the AC fees your truck's inverter at which point it's converted back to DC again to be stored in the battery. This is inefficient... so you're losing about 15 to 20% of the solar power just due to the conversion. To my knowledge there is no way to take DC from a solar panel and jam it directly into a EV Battery as DC storage.
