If I read your post right, you are installing insulation inbetween the rafters?
This is not good without the vents with fiberglass insulation. You would need the soffit and ridge vents.
If you are insulating the attic floor, you will be fine with the attic gable end vents installed where the windows used to be.
Make sure any vapor barriers you install go to the heated side, this would mean you should use paper face fiberglass with the paper touching the plaster or sheetrock backing.
Another solution to all the attic insulation is a product called nuwool. Then you need no venting.
I try to keep it simple, if you are unsure, contact your local building official or hire a home inspector by the hour for solid advice on what you are doing...if you are still unsure.