Hi Lindsay,
As the mama of a kiddo with some special needs myself, I understand your desire to do all you can to help your daughter be comfortable during her vacation. I'm happy to share with you what I know so that you can make the decision that's best for your Mouseketeer!
First,
Rock 'n' Roller Coaster Starring Aerosmith is a super fun, thrilling adventure that does have quite a bit of noise. When your super-stretch limo takes off, you'll hear Aerosmith shouting a countdown to get you to the concert on time, and classic Aerosmith songs provide a soundtrack to your adventure during the ride. You'll hear occasional fan cheering sounds, too, but there won't be sudden noises other than any squeals or screams from other Guests sharing your ride.
I called
Disability Services to ask if your daughter would be able to keep her noise-canceling headphones on during the attraction, and since the attraction includes upside-down inversions, they recommend
not wearing headphones during it, but won't prohibit her from doing so. If she does choose to wear the headphones and they fall off during the ride, it's possible that she might not get them back or that it could take several days for them to be found. The attraction itself lasts about a minute and a half, so it would be up to you to decide if you'd like to try to use the headphones or if you'd rather take them off as she's boarding the limo and store them safely during the ride. There are over-the-shoulder safety restraints, so I don't think it would be possible for her to either cover her ears herself or hold on to the headphones.
I hope this helps you decide what's best for your princess, Lindsay, so that she can have a rockin' great time!
Missy