Tight rear naked choke. It is an easy way to submit your opponent, or render them unconscious if necessary.
Check it out in this short video:
Of course them rolling onto their front is ideal for you, as you then have the opportunity to sink the choke.
While you're spinning them slide quickly to the left behind them.
Rain Defence more.
When applied as a blood choke in particular, it immediately reduces the supply of oxygen to the brain, leading as mentioned above to unconsciousness and ultimately if not released to brain damage or death.
Then double grabbing the forearm bone but hook your elbow around theirs for extra pull and pull it down the arm behind the head.
The left arm then reaches to the back of their head, far enough down so they can't simply reach up and remove your hand.
In the video and below I show you 5 of my favourite ways to finish the RNC against a dropped chin — check them out!