Self myofascial release of the hamstrings assist greatly with hip range of motion.
Increasing relative slide between the hamstrings can improve pain-free depth within squatting and hip hinging movements.
One of the easiest and most effective ways to get into the hamstrings with a ball is from the seated position.
Skip to the 5:00 mark here for a video demonstration.
Get a lacrosse or baseball. Don't go till the point of bruising.
There should be no numbness or tingling created. Move the joints above and below the balls contact for added benefit.