I don't want to disappoint you, but I have never been able to remove burnt-on pepepr juices - and in my case, they are on stainless steel, which can be cleaned with much harsher methods than non-stick. Most of the stuff went away, but small spots remained on my pot too.
I would advise to leave out all scrubbing. It is not very efficient even on steel, and it can easily damage a non-stick surface. Non-stick happens to be a chemically inert molecule, but it is very susceptible to physical damage.
The nice side of "chemically inert molecule" is that it can withstand a lot of chemical solvents - and these are better for burnt-on stuff anyway. I would go in there with concentrated acid first (citric acid solution at around 2 pH - try it in the same way as decalcifying a kettle, but use a higher concentration than written on the sachet), then, after a really good washing, switch to a base (for example a very concentrated baking soda solution, I would be afraid to use lye on a non-stick pan because it could seep through scratches to the interface between alu and non-stick surface and start corrosion spots). If that doesn't help, probably nothing will.
And I would strongly recommend to not roast peppers in a non-stick pot. Roasted peppers need very high temperatures. Non-stick coatings start changing their properties at around 250°C, this is a low-to-middle hot setting on most stoves (my resistive stove goes from 1 to 9 and 4 is already too hot for non-stick). The best method is a broiler in the oven, but if you don't have that, you can consider using a steel or iron pan which you don't mind accumulating some discoloration and spots (they are not too problematic on steel), or putting alu foil directly on the (resistive) hob and discarding it after the roasting.