I notice that alot of schools including mine roll from the knees. I'm interested as to what the first few parts of your game plan are when you start in this position? Everyone at my gym seems to do the same things, so I'm assuming everyone has a little pathway they usually follow to get going. Personally, I start sitting on one side of my butt, one hand on the floor and the opposite knee up. This means to me they can only pass on one side. If they put a knee up - I'll grab their ankle and the side of their head and go for the sweep. If they go to their open guard - I'll usually try to get ankle control, put them flat on their back and work some standing guard passes from there. If they stand - I'll go to a Tomahawk Sweep(hook behind one leg, other foot in the hip, wrist control with one hand and control the hooked leg with the other wrist, extend the leg in the hip and chop in the hooked leg to complete the sweep) and failing that, pull myself in, hip up, wrap my leg inside and around thier leg and go to the heel hook.