You’re not the only one, while in Japan I got wrecked a lot by Rolentos. Granted I’d run into the hidden boss Nemo every once in a while, but I generally felt lost in the matchup.
To me it feels like Rolento is just running around waiting for you to fall into one of their MKD baits. I felt like I did a lot better when I just played very aggressive, instead of hanging back and trying to get some footsies going.
That’s all I can really help with, sorry man. I feel just as lost as you do in the MU 
Yeah I feel like whenever you try to get the footsie game going his rolls and knives just kind of negate it. Well someone at my locals plays him and I’m going to be going into the lab a LOT versus this character so I’ll post anything I find.
Buffer the rekka from a crouching jab and it’ll stop the rolls, you’ll trade at worst case scenario.
Grapplers(Gief, Hawk, Hugo) are definitely my worst MU in this game. I just dont know how to handle them whatsoever. It’s never due to me playing footsies with them and losing, because they dont need to, and in the very few cases I play a non shenanigans grappler, I tend to be ok. Of course those matches are very few and far between online. Usually what happens is that I get into lp rekka range and they’ll jump in with their best jump in normal and it beats fei’s dp 90% of the time or it trades not in my favour. If I’m outside of lp rekka range, they’ll jump from the furthest distance where either their normal will beat feis dp in most situations, they’ll jump and not press anything to bait my dp, or they wont press anything and go for a cmd grab. The only AA I’ve had any success with is his st roundhouse, but even then it tends to trade(not as often as feis dp, but still) and even then the trade still wont be in my favour anyway. I watch guys like fuudo and mago play the grappler MU and their dp’s always beat grapplers clean, so I’m not sure what I’m doing wrong…
Of course once they get in, it’s pure 50/50’s into knockdown vortex until I’m dead. It’s the most frustrating thing, because there is no level you have to be at to beat me if you pick a grappler. You could have literally just started playing FG’s, pick a grappler, and It’s pretty much a wrap.
Also regarding the crouching/stand jab buffered into rekkas, are two jabs supposed to come out or only one? I notice in Fuudo’s matches only one seems to come out…
If DP is losing or trading you probably need to do it later or you just aren’t playing the match up in a space where DP is great. Try doing it later before assuming it doesn’t work in that range, and don’t forget if it is trading a lot you can chicken wing after for more damage. Also watch this video and really listen to the commentary.
Grapplers are for sure tough, and you need to rely a lot on normals rather than specials. Be comfortable with standing in LP Rekka range and not using it…ever. Only once you’ve shown the other player that you can out normal him will he hold db and you can Rekka (sparingly).
Stand jab is your friend, tap it, plink it with hp Rekka buffered, double tap it, whatever you have to do. 9 tims out of 10 it will catch whatever normal they threw out.
As far as AA’s go, the normal should never win out. Your timing is off, you have to be comfortable with letting them jump deep before DPing. If anything, use the EX as it has one extra frame of invincibility. I’ve always maintained a SFII mentality of “if it flys it dies” thing cuz if it’s in the air it can’t block.
Practice with Ryu or Ken and their j RH, people block it but you shouldn’t. Or better yet, Zangiefs j Fierce, you have to wait till they’re really deep into the jump ark. A knee jerk reaction DP will get stuffed. It’ll be good practice for people who like cross up tatsu to try and get out of the corner. Speaking of which, cross up tatsu is your best bet for learning to be patient with the DP
Hope this helps a bit