You can drill a lot your movement skills and even shadow reaction drills. These are just tools for your roll. Actual roll you need a partner and be sensitive of his pressure, balance and handles he gives you to manipulate him.
So today I'll watch some clips (actually rewatch and try to memorize) and then shadow roll and repeat the moves with focus on triggers that starts my movements. (So I need to imagine my posture and grips, but also what opponent has and is giving me. Totally unrealistic, but it's a step. Not a final technique.) More like rehearshal for an experiment and experiment will continue first with a co-operative opponent and finally in an alive roll.
(Isolation drill is a term that SBGi uses for none resistance technical rehearshal to learn a move/technique.)
I could also do some techniques for purple belt test....just isolation solo drilling...two years before the test...
My fundamental movements
I did try to make a list yesterday on what could be useful to drill - for me.
1. Technical stand up ( lifting hip up to gain momentum before stepping back
2. From flat on back ("grilled chicken") to sit up to low single leg takedown
3. Grilled chicken - basic 360 movement and "knee rule" aca crazy legs
4. Scrimb all directions
6. Wrestlers sit thru from putt up all fours
7. All ukemis
8. All shadow boxing, grappling and judo