The trick with roll off is, being able to reach your posts' (all three) right,left, and isolator. You never know when you may have a free flow. As far as your dry suit inflator, not having a bottle of argon or at least air tends to get cold with a 35% helium mix. Not sure where you dive, but when I'm at 150' + it gets damn cold. My suggestion would be, contact your LDS about tech diving and the ramifications of doing so. Not that tech diving is dangerous, but, there requires much more preparation involved.
Dive safe/Train hard
Joe
Dive safe/Train hard
Joe