So I'm currently about half-way through WC3 (stuck there, see my other post LOL) and will then continue on to WC4 -- and I really would rather play these great games on my TV, without a keyboard in front of me.

My question is: if I were to theoretically buy something like this: http://a.co/9xKBpEM
would I be able to make it successfully work with WC3 and WC4 as intended?

Will the throttle and roll controls work as expected?

Yes, but it requires a bit of fiddling with the Thrustmaster T.A.R.G.E.T. software and some modding/patching with WC3 (WC4 doesn't require patching).
Here's a thread for patching WC3:
https://www.gog.com/forum/wing_commander_series/wing_commander_iii_win95_version/page1

After patching there is to be said that the set you have liked is ideal because it has a software that allows to use the full set with games that nominally support only one peripheral with a very limited number of buttons.
You are going to need it for both these games, but once done you'll be able to play without using the keyboard.
Bascially you will have to use the software to convince the game that the throttle piece is the "z" axis of the main joystick, I don't remember if they support rudder control (I played WC4 last a few years ago with my HOTAS so I'm not 100% sure it supported rudder as well and I haven't tried WC3 with the patch yet) but you just have to be sure that your desired rudder axis is marked as the "R" axis and disable all remaining axis.
For mapping the buttons I sugget you leave the fire buttons as normal "directX" buttons (if not the game might act funny) and use the software to map all the other buttons and 4-way switches, you should be able to map everything so you won't need to use the keyboard for anything.

Thanks for this reply... I will definitely go ahead and order it then... I was reading about the TARGET software, but still wasn't sure if it would work with these games, and you answered my questions.

I used TARGET and this stick (I have basic version, so no HOTAS) to make Wing Commander 1 to play more like more modern space sims. Only thing I could not get to work was slider (when I set it as pulse, the speed was controllable, but changing it was near impossible, mapping it as Hold ended with easy changing, but nearly no control, speed was increasing or decreasing way to fast), so I mapped speed increase/decrease to hat. Have the same issues with Descent, I believe there is a solution, just have no idea what it is.

With Descent it should be actually a bit easier since it's more like a FPS (throttle tull ahead presses "go forward" and throttle full backwards presses "go backwards", you just need to script a bit of a deadzone in the middle), with Wing Commander I did a script for my HOTAS in CH Control Manager (like TARGET but for CH Products peripherals) but yeah it doesn't really work that well in a game with a aircraft-like throttle.
With Descent you can use DXX-rebirth which allows multiple peripheral support and control mapping, if you prefer old style graphics you can fiddle with the options to have the old look (personally I went with an intermediate solution: 1920x1080 with max anti aliasing but with unfiltered textures) there are some issues with implementing CD music though.

Problem with Descent original is that it looks like it is either full speed forward or full speed backward, it is hard (or impossible) to move slower. DXX-Rebirth has working throttle function and there it is possible to move with different speed.

WC main issue is that the game was never designed to use throttle axis, so it is not really surprising it is hard to map. At least it was way easier to map banking to handle twist axis.