If it is a "warm roof" unvented or the venting is on the outside of the insulation the best system is to insulate the underside of the roof.

If you have insulation on the sidewalls and attic floor and the space space between the roof and attic floor vented there are lots of sneak paths between the pony walls and floor.

Bill is correct. Your roof's construction will dictate how you should insulate. Do the right thing or you risk premature shingle life and structural damage.

thanks for you input. so what you are saying is i should tear off the insulation on the roof and insulate the knee wall and floor of the attic. i am not sure yet but what i have heard so far is i must insulate the roof area above my crawel space and put baffles in between the insualtion and the roof. it my also be a good idea to add soffets vents near my gutters.