My problem is no matter how many times I wash my hair and use medicated shampoos for psoriasis I still get flaky scalp and painful root folicals why?

Psoriasis is chronic. Unfortunately, psoriasis is treatable, but not curable. Symptoms can be minimized by medications, but intermittent flares should be expected. If your condition has never improved with the previous medical treatment offered to you, reconsider the primary diagnosis of psoriasis.