never done it, nor coached anyone to do it, mate. If I was to give it a go I'd get super good at sets of rollouts on my knees (like 20 reps).
Next step'd be kneeling on an aerobics step or something. This is as far as I've gotten in the past.
The problem then is the jump from kneeling to standing is fucking huge in terms of difficulty, even with the step of using the, well, step. I was never patient enough with it and have always given up at this point.
How I think I'd approach it though were I to give it another try would be some sort of ROM progression, gradually letting the reps get deeper as you get stronger. I know some people do this using a wall to stop the roller getting out too far. I dunno; seems like a recipe just to go slamming roller-first into the wall, but having never tried it I can't really comment on it.
So, for what it's worth, that's what I'd do.
Someone like @Chris_Colucci would probably be able to coach it better than I.