Cold floors and drafts
I'm going to assume that the attic is for storage and isn't needed as a "conditioned space". 


Remove the insulation from the roof. It's detrimental to ventilation and cooling in the summer and won't do you much good in winter. 
Insulate the attic floor. You can probably reuse your roof insulation, and as little as R-19 will probably solve your problem for all but the very coldest days, but ideally you'll get to R-30 or better. Also insulate the attic trapdoor with foam sheets or whatever, and seal it against air leakage.  You can still use the attic for storage, but the floor may need to be lifted to accommodate the insulation.
Improve attic ventilation. Ridge venting is part of the system. You also need soffit venting or something else low in the roof. Ideally you have a flow path that moves air upward and out across the entire attic area. It's critical to vent heat in the summer and moisture in the winter. 


It's that simple. Let us know in a comment or an edit to your question if this isn't feasible for some reason. The uninsulated floor isn't ideal, but it's a minor component of your overall problem.