The H MF grab resets in the corner are very clever. Good stuff.
About tech/roll directions: You don’t have to be psychic to predict the direction they recover, most people have habits you can find out about during a match. You’ll have to discover those habits and apply mixups proper for the direction you know they’ll recover. Some people do like to change things up, though.
Having said that, you can do left/right mixups from techs. One thing I was disappointed in not seeing in your video, on the air grab corner resets, is when the opponent techs forward (to behind X-23, holding H Mirage Feint), you just go air grab them. If you can get behind the opponent, like you did, you can go for a full combo instead. And getting behind people teching is something super easy for X-23. Her ground dashes essentially have the length of anyone’s tech (a bit more, and also the length of a roll), so you can create some very easy left/right mixup situations. Hell, if you know the direction (though you can react if you pay attention) of the tech, you can dash under once then dash under again, no wavedashing needed. The coolest thing about it is that X-23 has millions of points in her usual BnB to suddenly stop the combo and apply this.
But one thing to mention is that double jumping/air-dashing destroys the air-tech resets.
As for roll resets, X-23 does have some good options. In the video there is a situation where the opponent rolls behind you when you want to do M Mirage Feint. One thing you can do is delay it, making an option-selectish input: if they roll behind you, the ankle slicer comes out. Catches people by surprise but unfortunately it’s not safe and ruins the timing for assists. Another option, as I mentioned, is how her dash is roughly the same length as a roll and so is her M Mirage Feint, as you noted. This means that in the corner, you can dash back to get forward rolls and then dash/MF forward into the corner again in reaction to backward rolls. Personally, I leave an assist there to keep people in blockstun if they roll back, giving me a little more time. Mid-screen, you can do what Tatsu is famous for: wavedashing on their heads, crossing them up millions of times until they actually stand up.
My personal resets: Do L MF instead of H MF during her BnBs, cross under, cross under again; Do three H MFs, during the third, do nothing, land, dash under; Instead of catching people with standing M after her L Talon Attack, I pretend I drop the combo and do just standing H instead then cancel into her command grab; Call an assist while I catch people after the L Talon attack, keep ground chain and finish with M MF, crossing up (DevilJin does this one too, I think); After a mid screen OTG, dash and call assist, L MF, L/M MF (the first one is to time with the assist); After a corner OTG, call assist, dash back - if they rolled away from the corner, attack, if not, dash back in and attack; Alternatively, just call assist after an OTG and do M MF, knowing that they will roll backwards.
… I wrote too much about myself. The video was great overall, did show me some cool things, but then I started pointing out stuff and got carried away.