Never felt the need in Descent, I either played keyboard only or recently (before buying the throttle) WASD + joystick (with up/down thrusters assigned to a hat), but I still have to try it with the full HOTAS.
Is FS Freespace or Flight Simulator?
With Freespace I never really felt the need for twist, and if it was Flight Simulator, well, I never managed to get into real aricraft simulators.
The issue for me is that if you're using a joystick but relying on keys/buttons for roll, you have two axes of rotation with full-on continuous control, but the third with an on/off binary, and that sort of discontinuity just doesn't work for me. I need the same sort of fine control across all three axes, particularly in a frenetic multiplayer game like Descent. Hell, I'd forgo the keyboard completely and go joystick-only, and indeed I did for many years, except my ancient 3D Pro's throttle slider kind of sticks at both ends and isn't as precise as I need it to be in the first place. Never did get how anyone managed with a keyboard-only config, even if some of the best multi pilots in the history of the game made it work.
And yes, I mean FreeSpace, and the reasons remain much the same as for Descent. Obviously both of these games are somewhat flipped from a normal flight simulator in that yaw is far more important than roll, but I still want that full-on analog control for the latter, and I'd sure as hell never want to delegate it to a pair of pedals.
Descent acts a lot like a FPS, the only thing that makes a joystick or keyboard more viable than a mouse for aiming is its 6DOF nature, and being at its core a FPS fine control isn't really that necessary as much as reactiveness, I've been trying using the analog axes with a HOTAS (via a source port that supports analog axes for throttle, thrusters, etc) and thrusters work better with digital inputs in that game because when you need them you need to be as fast as possible rather than precise.
I never used roll during combat in Freespace, it's just a waste of time, even more than in X-wing as the gun racks are usually closer toghether with few exceptions.
Sincerely playing FS joystick-only is inconceivable to me, most joysticks have too few buttons for a spacesim (too many essential functions), the only games I ever played joystick only are the two Rebel Assault games (which are essentially rail shooters) and Rogue Squadron 3D (which was made with a N64 controller in mind and then ported to PC).
And no, I've never used pedals as roll in essentially all the games I'm interested in is not really necessary. Call me a dinosaur but I grew up in an era when sticks with twist were rare, pedals were for rich people and the most complex sims (and even most of them didn't support analog yaw, I've never known anyone to have pedals at the time), and everyone was used to the classic "hold button 2 to roll" or used the keyboard (on which you had to keep a hand anyway because even an 18-button Combatstick has too few buttons for a game like X-wing ad at the time 4-button sticks were the norm), the twist rudder became really common only after Freespace 2 came out.
Yeah, I can't see myself using pedals. After 17 years of joystick twist, there's no way I could go for them now. 
You definitely need something to roll with in FreeSpace, though. Using X and Y constantly to correct sounds like excessive work.
Hhhm, I always wonder why people find rolling that necessary on a spacesim that isn't Elite: Dangerous, keyboard rolling is perfectly fine in FS at least for the few times I bother using it.