Disclaimer - YMMV.
There are lots of people on thie board who may want to post the facepalm picture after reading this. To those people, I suggest you skip this post, or douse yourself with your sense of humor.

I deleted all my pix, so sad.

The rollers, and the headwind unit have rectangular hollow legs, so it was easy to fashion wooden pegs out of a 1x1 piece of lumber that fit snuggly inside the legs. I have good carpentry tools so getting the lengths even was not a problem. I used wooden shims where necessary to get a snug fit.

I drilled an axle hole into each of the pegs (6 for the rollers, 2 for the headwind unit) to accomodate a 5/8 diameter bolt.

I poked the wooden pegs into the legs of the roller with the axle holes properly oriented.

I bought off ebay a set of 10 skate board wheels and a matching set of bearings.
At the hardware store, I bough a bunch of 5/8 bolts of the proper length, and a bunch of washers, also, nuts.

I poked a bolt through the axle hole in the peg, set up some washers to engage the skateboard bearing, added the skateboard wheel. applied more washers, and then the nut. Repeat for 5 other legs.

Took two long shelves and one short one.
created an H pattern so that the rollers run on the long shelves, and they are connected in the center with the short shelf. Standard hardware for attachments.

Screwed eye hooks into the fore and aft edges of the center shelf. Got 2 old innertubes and routed them thru the eye hooks and around the roller legs to create for and aft tension. I may have used some string for the attachments to the eye hooks.

The headwind unit took some additional creativity to get everything lined up and rolling, but the same idea. I used a single axle for both feet, and stacked the axle with a wheel, 1 foot, a spacer, a center wheel, more spacers, another foot, and a third wheel. overkill, but hey -I got 3 wheels!

Let me know if that makes no sense whatsoever. I'll can take pix later if you ask for them.

By the way, I also made a removable post for leaning on:
2 2x4's screwed together, a frame unit attached to the ceiling to accomodate the post, and a slab on the floor with wedges to put the system in compression. It's removable by removing the wedges. There's a small shelf for TV remote volume control, glasses, and a water bottle. I also made a stool with a floor and a hollow interior to store my shoes, and as an aid for mounting and dismounting, since the entire system is elevated beyond my ability to straddle the frame with my feet on the floor.

This is my longest post ever! >celebration<