A paint stencil seems impractical and expensive. This is a simple pounce pattern job. It's just big.
I would make 3 or 4-foot wide by 25-foot long pounce patterns and then tile them side by side. The transferred charcoal lines will be plenty good enough for professional painters to follow. Even then, the edges need not be crisply perfect since the graphics will be viewed from the air. Edges could be cut in with 3 or 4-inch cutters, or even 3-inch rollers, then filled in with large rollers. 2-inch tape could be used on long straight lines, if needed, but I probably wouldn't bother. Cutting lines by hand at that size is quicker.
Once you are up on the roof, position and tape down the center pounce pattern first. This first pattern must be positioned perfectly, of course. Dust it with charcoal, then align and tape additional patterns on either side, dusting as you go, till the entire 150-foot design is transferred to the surface.
I did a similar job on the side of a large building two years ago out of a bucket truck by myself (and I am very old). I carefully positioned the top of the center pattern and unrolled it downward, taping as I unrolled, after which I dusted with charcoal from bottom to top as I ascended back up to the top. Then I was ready for the second pattern to be positioned on the wall next to the first, taping it down as I descended, then dusting with the pounce bag as I ascended. Working from the center to the right, and then from center to left, I was able to transfer the entire layout to the wall by noon and then started painting. Transferring the design took three setups of the truck, and I moved it again three times for painting. I could have painted the middle section before pouncing the rest of the layout, but I wanted the entire design to be on the wall before painting. (I don't always trust my math). As it was, I moved the truck six times instead of three. Toward the end of the first day's painting, I also went over all the remaining lines with a Sharpie marker before I went home, as there was a chance of rain which could have washed off the charcoal lines.
Your roof job should be no more difficult than hand lettering a wall, and you won't have to fight gravity or make multiple setups of a lift. Wind can be a factor, but Gorilla tape to hold the patterns is pretty secure.
I would use the heaviest pattern paper practical for your plotter. If your plotter can't perforate the paper it can be perforated by hand with a large pounce wheel, but you will have sore fingers. Mark the center pattern and number the rest of the patterns left and right from the center out. If you end up with 50 patterns you will want to keep them from getting mixed up.
This is not a super complicated job. And it is an opportunity to make a nice chunk of cash for the cost of a roll (or two) of kraft paper, whether they apply the paint or you do. This is just a large billboard lying down. Your back will be sore. If you do the painting, do as much rolling as possible using broom handles on the rollers so you can work standing.
You could even show the painters how to tape down the patterns and tile them side by side so that all you would need to do is make the patterns. They would probably do just fine.
