I've used rollers for many years, and would have a few comments:
First of all, that YouTube free motion thing looks like a great idea! I'll be noodling on a best way to do that. Mounting the rollers inside another frame, allowing relative motion of the roller unit with the floor, would seem to help in the transients (i.e. acceleration, standing, etc.). Good idea there.
Second, yes - I would suggest adding some type of load to the rollers, but I would never do the towel or carpet thing. This is just me - those ideas just seem to kludgey to me. You'll be creating dust, wearing things out quickly, constant replacement, carpet particles flying everywhere, static electricity, .... yuk.
There are many choices of load units for rollers - mainly magnetic & wind.
I have Kreitlers, and use the squirrel cage fan unit for resistance.
I would seriously recommend adding an element of inertia to the rollers too. You want to replicate the inertia you have while moving down the road, while stationary on the rollers. So, you're basically exchanging rotating inertia in the form of a flywheel for the linear inertia you have while moving. Kreitler offers flywheels, which help in replicating a real pedal stroke immensely!
I sometimes use two at once, although that setup (with the fan) is quite a load.
You could you the same by adding evenly distributed weights around the outer circumference of your wheels too. You'd have to come up with a simple way of putting them on and taking them off, though. Or, just have one set of roller-specific wheels with permanently attached weights.
The Kreitler setup (fan + single flywheel) offers a resistance like about a 10 mph headwind or so. That's with the fan opening (resistance adjustment) set at zero. It can be opened up to create greater drag. The resistance settings that Kreitler puts on the outside of the fan adjustment are inaccurate, being under-estimated.
Before I had the Kreitlers, I had a cheaper plastic drum set, and used a magnetic resistance unit, which I found to be OK.
If you have a cheaper roller set (plastic drums, etc.) I would HIGHLY recommend replacing it with Kreitlers when it wears out.
Good luck, and have fun !!